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Intro Classes > Genetics > Flashcards

Genetics Flashcards

1
Q

gene

A

a DNA segment with a nucleotide sequence encoding an RNA product that is either directly functional or encodes a protein

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2
Q

locus

A

location of a gene or a particular DNA sequence (e.g., promoter) on a chromosome

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3
Q

allele

A

one of the variant forms a gene can have in a population (from a particular locus)

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4
Q

wild-type allele

A

the allele that encodes for the most common phenotype in a population

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5
Q

mutant allele

A

any allele that does not code for the most common phenotype in a population

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6
Q

multiple alleles

A

the occurrence of more than two different alleles in a population (e.g., the ABO blood group system)

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7
Q

allele frequency

A

the prevalence of a particular allele at a genetic locus within a population

E.g. If 10 individuals of in a population of 250 individuals (total of 500 gene copies) are homozygotes and 30 are heterozygotes for a certain mutant allele, then the total number of mutant copies is (10 x 2) + (30 x 1) = 50. Thus the allele frequency of the mutant allele will be 50/500 = 0.01 = 1%

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8
Q

genetic polymorphism

A

the presence of two or more variant forms of an allele for a gene that can occur among different individuals or populations

the most common type involves variation at a single-nucleotide polymorphism (SNP), but can be much larger, involving longer stretches of DNA

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9
Q

chromosome

A

a structure found in the nucleus of eukaryotic cells that contains part or all of the genetic information for a given organism

comprised of nucleic acids and associated proteins (e.g., nucleosomes)

each human cell contains 23 pairs of homologous chromosomes (corresponding in structure and genetic information, i.e., 23 chromosomes are inherited from each parent)

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10
Q

allosome

A

AKA sex chromosome; a type of chromosome that carries the genes that determine chromosomal sex

human cells contain one pair of allosomes: XX in female individuals and XY in male individuals

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11
Q

autosome

A

any chromosome of a cell genome that is not an allosome (sex chromosome)

human cells contain 22 pairs of homologous autosomes

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12
Q

ploidy

A

the number of chromosome sets present in a cell

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13
Q

haploid cell

A

contains one single unpaired set of chromosomes (n = 23)

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14
Q

diploid cell

A

carries a complete set of paired chromosomes (2n = 46)

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15
Q

chromatid

A

one of the two identical strands of a replicated chromosome

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16
Q

sister chromatids

A

two identical chromatids joined at the centromere (i.e., the duplicated chromosome)

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17
Q

centromere

A

a condensed region of chromosomes where sister chromatids join and mediates attachment of the chromosome to the meiotic or mitotic spindle

divides the chromatids into a short p arm and a long q arm

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18
Q

metacentric

A

due to the position of the centromere, the p and q arms of chromosomes are of approximately identical length

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19
Q

submetacentric

A

due to the position of the centromere, the p arm of the chromosome is short and the q arm of the chromosome is long

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20
Q

acrocentric

A

due to the position of the centromere, the p arm of the chromosome is much shorter than the q arm the chromosome

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21
Q

kinetochore

A

a protein complex found at the centromere that allows for the attachment of mitotic spindle microtubules during mitosis

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22
Q

telomere

A

repetitive, noncoding DNA sequence at the ends of each chromosome, which prevents the loss of coding DNA sequences during DNA replication

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23
Q

telomere shortening

A

occurs after each cell division; can reduce a cell’s life span

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24
Q

mutations

A

alterations in a cell’s genome

may have endogenous causes (e.g., errors in DNA replication, cell division, and/or DNA repair mechanisms) or exogenous ones (e.g., a variety of physical, chemical, and biological agents)

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25
Q

germline mutation

A

AKA gametic mutation; a mutation of germline cells that can be passed on to offspring

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26
Q

somatic mutation

A

AKA acquired mutation; a mutation of somatic cells that typically affects only one allele of a gene

since it does not occur in a germline cell, cannot be passed down to offspring

common mechanism for carcinogenesis

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27
Q

mosaicism

A

the presence of two or more populations of cells within an organism, each with a different genetic composition

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28
Q

chromosomal mosaicism

A

the presence of cell populations with different karyotypes in one organism

E.g. sex chromosome mosaicism is frequently seen in Turner syndrome (i.e., one population of XO cells and one population of XX cells)

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29
Q

gonadal mosaicism

A

the selective presence of a mutation in individual germ cells; caused by a mutation in the DNA of a primordial germ cell during mitosis

Clinical application: Suspect this type of mosaicism if no blood relatives of the affected individual have the condition

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30
Q

somatic mosaicism

A

the selective presence of a mutation in individual somatic cells; caused by a mutation during mitosis after fertilization

usually, multiple tissues or organs are affected

E.g. McCune-Albright syndrome

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31
Q

chimerism

A

the presence of two genetically distinct cell lines that arise from two different zygotes that fused into one single embryo

[two cell lines sharing an embryo, like multiple animals sharing the body of a chimera]

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32
Q

chromosomal instability

A

a chromosomal state characterized by increased susceptibility to mutations; caused by mutations of DNA repair genes

results in multiple chromosomal translations, inversions, and deletions among daughter cells

E.g. Fanconi anemia, ataxia-telangiectasia

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33
Q

loss of heterozygosity (LoH)

A

loss of a normal allele of a gene with the exclusive expression of the abnormal allele

the occurrence of LoH in tumor suppressor genes leads to malignant transformation of the cell.

E.g. Lynch syndrome

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34
Q

two-hit hypothesis

A

states that two mutations (i.e., “hits”) must occur in the cellular DNA of tumor suppressor genes to induce oncogenesis (but does not apply to oncogenes)

first hit: One copy of a tumor suppressor gene is inactivated by mutation or epigenetic changes, and the cell becomes heterozygous but the second allele is functional and produces a normal tumor suppressor protein.

second hit: The second copy of a tumor suppressor gene is inactivated by the mutation, and LoH occurs (the cell becomes homozygous). No tumor suppressor protein is produced leading to increased risk of oncogenesis

E.g. retinoblastoma, Li-Fraumeni syndrome, Lynch syndrome, familial adenomatous polyposis

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35
Q

del

A

deletion

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36
Q

dup

A

duplication

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37
Q

46,XX, dup(q3)

A

duplication of the long arm of chromosome 3 in a female individual

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38
Q

46,XY, del(p5)

A

deletion of the short arm of chromosome 5 in a male individual

E.g. cri-du-chat syndrome

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39
Q

inv

A

inversion

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40
Q

46,XY, inv(3)(p23q27)

A

pericentric inversion of the chromosome 3 segment with breakpoints at position 23 on the short arm and 27 on the long arm in a male individual

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41
Q

t

A

translocation

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42
Q

46,XY, t(14;18)(q32;q21)

A

translocation between position 32 on chromosome 14 and position 21 on chromosome 18 in a male individual

e.g. follicular lymphoma

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43
Q

rob

A

Robertsonian translocation (a chromosomal translocation that involves the fusion of the long arms of two acrocentric chromosomes at the centromere with resulting loss of the short arms of the involved chromosomes)

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44
Q

46,XX, rob(14;21)

A

chromosomal translocation with the fusion of the long arms of the acrocentric chromosomes 14 and 21 in a female individual. The short arms of the two chromosomes involved are lost

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45
Q

chromosomal aberrations

A

mutations affecting large segments of DNA

can be detected by FISH (flourescence in situ) and not karyograms

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46
Q

numerical chromosomal aberrations

A

the presence of an abnormal number of copies of a single chromosome, which is usually caused by the failure of homologous chromosomes to separate during mitosis or meiosis (nondisjunction)

detected through a karyogram

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47
Q

aneuploidy

A

an abnormal number of chromosomes or parts of a chromosome within the cell

[an = not; eu = good; ploidy relates to chromosome number]

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48
Q

hypoploidy

A

the presence of fewer chromosomes within a cell compared to the expected number

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49
Q

monosomy

A

presence of a single copy of a chromosome

usually results in embryonic death due to the high probability of recessive trait expression of the respective chromosome (exception: Turner syndrome, which is characterized by a 45,XO genotype)

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50
Q

hyperploidy

A

the presence of extra chromosomes within a cell

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51
Q

trisomy

A

the presence of a triplicate instead of a duplicate set of chromosomes

E.g. trisomy 21 (Down syndrome), trisomy 13 (Patau syndrome), trisomy 18 (Edwards syndrome)

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52
Q

polysomy

A

the presence of ≥ 3 copies of a chromosome in a cell

E.g. trisomy, tetrasomy, pentasomy

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53
Q

structural chromosomal aberrations

A

an alteration of a chromosome structure with an identical number of chromosomes

(ALL translocations are classified as structural chromosomal aberrations)

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54
Q

deletion (chromosomal)

A

a loss of a chromosome segment

E.g.
cri-du-chat syndrome, which is characterized by 46,XX, del(5)

myelodysplastic syndrome, which is characterized by 5q deletion

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55
Q

duplication

A

duplication of a chromosome segment

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56
Q

inversion

A

chromosomal rearrangement involving end-to-end reversal of a chromosomal segment

E.g. 46,XY, inv(3)(p23q27)

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57
Q

chromosomal translocation

A

relocation of one chromosome segment onto another (non-homologous) chromosome

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58
Q

balanced translocation

A

a type of translocation in which no genetic material is lost or duplicated, thus expressing a normal phenotype

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59
Q

unbalanced translocation

A

a type of translocation in which genetic material is lost or duplicated, thus expressing an abnormal phenotype

can result in chromosomal imbalance (e.g. Patau syndrome), multiple malformations, stillbirth, and repeated miscarriages

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60
Q

Robertsonian translocation

A

a chromosomal translocation that involves the fusion of the long arms of two acrocentric chromosomes at the centromere with resulting loss of the short arms of the involved chromosomes

one of the most frequent translocations, and may be balanced or unbalanced

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61
Q

balanced Robertsonian translocation

A

the translocation between the long arms of the chromosomes occurs and the karyogram shows a total number of 45 chromosomes but results in a normal phenotype (pt is a carrier)

E.g. translocation of 21q to 14q with the elimination of the p arms

affected individuals inherit a balanced translocation from their phenotypically normal parent

pregnancies with balanced translocations have an increased risk of miscarriage, and children of carriers of balanced translocations are at higher risk of acquiring unbalanced translocation

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62
Q

leptotene

A

stage of prophase I (meiosis) during which chromosomes condense and become visible, and then the chromosomes attach to the nuclear envelope

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63
Q

unbalanced Robertsonian translocation

A

clinical features of trisomy 21 caused by inheritance of a translocation chromosome and a normal chromosome

although there are only 46 chromosomes present, three copies of genetic material from chromosome 21 exist

results in the karyotypes 46,XX,+21,t(14;21) and 46,XY,+21,t(14;21)

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64
Q

reciprocal translocation

A

a translocation between nonhomologous chromosomes

E.g. Philadelphia translocation

[you ask a favor (reciprocation) from strangers (nonhomologous)]

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65
Q

uniparental disomy

A

a chromosomal abnormality in which offspring receive two copies of one chromosome from one parent and no copies from the other parent; cannot be detected via karyotyping because the number of chromosomes is normal and there is no loss of genetic material

may be caused by errors in meiosis I (i.e., heterodisomy), meiosis II (i.e., isodisomy), or trisomic rescue

usually results in normal phenotype and euploidy in affected individuals and should be suspected if an individual presents with an autosomal recessive condition but only one parent is a carrier

E.g. Angelman syndrome (5% of cases); Prader-Willi syndrome (25% of cases)

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66
Q

isodisomy

A

when an individual has two identical homologous chromosomes inherited from one parent

either occurs in meiosis II d/t nondisjunction, or as a postzygotic chromosomal duplication that leads to duplication of one chromosome of one pair and subsequent loss of the other partent

[“I”sod”I”somy: meiosis “II” error]

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67
Q

heterodisomy

A

when an individual has two different homologous chromosomes inherited from one parent

error in meiosis I d/t nondisjunction

Heterod”I”somy: meiosis “I” error

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68
Q

trisomy rescue

A

when a cell containing three copies of a chromosome from nondisjunction loses one of those chromosomes, resulting in two chromosomes

if both of the remaining chromosomes are from the same parent, this results in uniparental disomy

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69
Q

12–345 (mnemonic)

A

the chromosomes most frequently involved in Robertsonian translocations are chromosomes 2”1”, 2”2”, 1”3”, 1”4”, and 1”5” (21, 22, 13, 14, 15)

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70
Q

genetic transition

A

the replacement of one purine with another purine (e.g., G to A), or the replacement of a pyrimidine with another pyrimidine (e.g., T to C)

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71
Q

genetic transversion

A

the replacement of a purine with a pyrimidine (e.g., A to C, A to T, G to C, G to T) and vice versa

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72
Q

trinucleotide repeat expansion

A

increased repetition of base triplets that leads to faulty protein synthesis or folding; characterized by genetic anticipation

E.g. Friedreich ataxia, fragile X-syndrome, Huntington dz, myotonic dystophy
[Friedrich gave the fragile hunter my tonic]

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73
Q

Huntington disease mode of inheritance

A

autosomal dominant

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74
Q

fragile X syndrome mode of inheritance

A

X-linked dominant

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75
Q

Friedreich ataxia mode of inheritance

A

autosomal recessive

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76
Q

myotonic dystrophy mode of inheritance

A

autosomal dominant

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77
Q

Huntington disease affected gene

A

HTT

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78
Q

Huntington disease chromosome

A

4

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79
Q

Huntington disease trinucleotide repeat and typical features

A

CAG

features: chorea, akinesia, cognitive decline, behavioral change

[a CAG trinucleotide repeat leads to Chorea, Akinesia, and Grotesque behavior]

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80
Q

fragile X syndrome affected gene

A

FMR1

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81
Q

fragile X syndrome chromosome

A

X

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82
Q

fragile X syndrome trinucleotide repeat and typical features

A

CGG

features: large protruding chin, large genitalia (testes), hypermobile joints, mitral valve prolapse

[a CGG trinucleotide repeat leads to an X-tra large Chin and Giant Genitalia.]

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83
Q

Friedreich ataxia affected gene

A

FXN

[Friedreich ataXia Nucleotides]

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84
Q

Friedreich ataxia chromosome

A

9

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85
Q

Friedreich ataxia trinucleotide repeat and typical features

A

GAA

features: ataxic gait, dysarthria, kyphoscoliosis, hypertrophic cardiomyopathy

[a GAA trinucleotide expansion leads to an ataxic GAAit and slurred words like GAA]

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86
Q

myotonic dystrophy affected gene

A

DMPK

[Dystrophic Musculature Produces Kyphoscoliosis]

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87
Q

myotonic dystrophy chromosome

A

19

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88
Q

myotonic dystrophy trinucleotide repeat and typical features

A

CTG

features: cataracts, premature hair loss in men, myotonia, arrhythmia, gonadal atrophy (men), ovarian insufficiency (women)

[a CTG trinucleotide repeat leads to Cataracts, Thinning hair (premature hair loss), and Gonadal atrophy]

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89
Q

in-frame deletion or insertion

A

deletion or insertion of three, six, nine, or more base pairs (always in triplets) without a shift in the reading frame, but with deletion or insertion of one, two, three, or more amino acids in the protein during translation

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90
Q

gain-of-function mutation

A

a mutation that leads to either the expression of the larger amount of the gene product or increased function of the expressed gene product

[make more or work better]

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91
Q

pathogenicity severity ranking of mutations

A

silent < missense < nonsense < frame shift

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92
Q

silent mutation

A

a point mutation that forms a triplet that codes for the same amino acid; often d/t a base change in the third position of codon (TRNA wobble)

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93
Q

missense mutation

A

a point mutation resulting in the formation of a triplet that codes for another amino acid

called conservative if the new amino acid is similar to the chemical structure of the original amino acid

E.g. sickle cell dz (glutamate -> valine)

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94
Q

nonsense mutation

A

nucleotide substitution that produces an early stop codon (UAG, UAA, UGA); usually results in a non-functional protein

(Stop the nonsense!)

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95
Q

frameshift mutation

A

deletion or insertion of a number of nucleotides not divisible by 3, results in misreading of all nucleotides downstream

protein may be shorter or longer, and its function may be disrupted or altered.

E.g. Duchesne muscular dystrophy, Tay-Sachs disease

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96
Q

splice mutation

A

an alteration (especially point mutations) in the nucleotide sequence required for splicing (e.g., the exon-intron border or at the junction)

results in defective mRNA (e.g., due to a retained intron) → shortened proteins that are either defective or exert an altered function

E.g. Gaucher disease, Marfan syndrome, dementia, epilepsy, some types of β-thessalemia

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97
Q

loss-of-function mutations

A

a mutation resulting in the expression of the gene product with decreased or absent function

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98
Q

null mutation

A

When a lost-of-function mutation occurs, and the degree of function is entirely lost

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99
Q

dominant-negative mutation

A

a gene mutation that produces a nonfunctional protein that exerts a dominant effect and impairs the function of the normal protein encoded by the wild-type allele in heterozygous individuals

E.g. mutant, nonfunctional p53 binds DNA and prevents the attachment of the functional p53 protein

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100
Q

epigenetics

A

the study of how an individual’s surrounding environment and behaviors influence gene expression and regulation, which is determined by chemical modifications of DNA bases (e.g., methylation) and histone proteins (e.g., various covalent modifications), which are carried out by specialized enzymes

epigenetic modifications influence the activation or deactivation of genes through reversible alterations to the chromatin structure but do not affect the DNA sequence or structure of DNA molecules

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101
Q

DNA methylation

A

the linkage of methyl groups to specific DNA cytosine bases with the subsequent formation of 5-methylcytosine

facilitated by DNA methyltransferases, and the resulting DNA segment has an unchanged genetic code but differs in epigenetic markers (e.g., methylation at transcriptional start sites) that alter DNA expression (inhibits transcriptional of the methylated gene)

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102
Q

DNA methyltransferases

A

a conserved enzyme family of cytosine methylases critical for epigenetic regulation that transfer a methyl group to DNA

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103
Q

process of DNA methylation

A

a newly synthesized DNA strand is methylated after DNA replication (using the matrix strand as a template)

in vertebrates, methylation most commonly occurs at CpG islands, a region of DNA enriched for repeating segments of a cytosine nucleotide that is followed by a guanine nucleotide, linked by a phosphodiester bond

methylation within the CpG islands will usually lead to repression of gene transcription

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104
Q

CpG islands

A

a region of DNA enriched for repeating segments of a cytosine nucleotide that is followed by a guanine nucleotide, linked by a phosphodiester bond

CpG islands are approx. 1000 base pairs in length, and many gene promoter regions are found within CpG islands

methylation within the CpG islands will usually lead to repression of gene transcription

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105
Q

inheritance of DNA methylation

A

specific methylation of CpG island transcription start sites can be inherited during somatic cell division and may be responsible for particular genomic processes (e.g., genomic imprinting)

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106
Q

Epigenetic regulation mechanisms mnemonic

A 
Acetylation Activates (DNA)
Methylation Mutes (DNA)

AA, MM

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107
Q

histone modification

A

the covalent bonding and chemical modification of histone proteins with various molecular moieties that alter the dynamic structure of chromatin and influence genomic regulation

results in the modification of the gene expression

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108
Q

types of histone modifications

A

deamination

ubiquitination

sumoylation

ADP ribosylation

phosphorylation

acetylation -> increased DNA transcription
deacetylation -> decreased DNA transcription
[Acetylation accelerates, deacetylation decelerates]

methylation - increased or decreased gene transcription

other modifications include histone tail clipping, citrullination, and serotonylation

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109
Q

inheritance of histone modification

A

the histone modification pattern is passed on to daughter cells during cell division

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110
Q

regulatory RNA

A

a diverse class of RNA molecules that play a role in the regulation of chromatin structure and gene expression

these RNA molecules are typically noncoding and do not produce translated protein products

gene regulation occurs via RNA-interference (RNAi) pathways

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111
Q

RNA-interference (RNAi) pathways

A

molecular pathways that use PIWI and Argonaute proteins to influence histone and DNA modifications with subsequent transcriptional inhibition

[Pee Wee Herman and the Argonauts forged a PATHWAY through hist-ory and the DNA of Greece mythology]

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112
Q

types of regulatory RNAs

A

long noncoding RNAs (lncRNA)

small interfering RNAs (siRNA)

micro RNAs (miRNA)

PIWI-interacting RNA (piRNA)

113
Q

unfortunate histone modifications examples

A

carcinogenesis: dysregulated histone deacetylases (HDACs) can decrease the transcription of cell cycle inhibitors (e.g., p21 in colorectal cancer) or cell differentiation factors (e.g., Runx1 in leukemia)

aging

114
Q

examples of regulatory RNA effects

A

X chromosome inactivation

genomic imprinting

transposon repression and silencing

115
Q

X inactivation definition

A

also called lyonization; inactivation of one of the X chromosomes in individuals with two or more X chromosomes (e.g., individuals with Klinefelter syndrome)

the selection of which X chromosome is inactivated occurs randomly, and prevents a toxic double-dose of X chromosome gene products

occurs early during embryogenesis with the affected X chromosome remaining inactive for the lifetime of the cell

116
Q

X inactivation proposed mechanisms

A

DNA methylation

Histone posttranslational modifications

RNAi via lncRNAs such as X-inactive specific transcript RNA (Xist RNA [seXist RNA]), a functional RNA product that coats the affected X chromosome and serves as the initiating and, hence, most important event in the inactivation process

117
Q

Barr body

A

contains the inactivated X chromosome packaged as heterochromatin which is transcriptionally inactive; located on the periphery of the nucleus

although most genes on the Barr body are inactive, some genes escape lyonization (X inactivation) and remain active

118
Q

manifestation of X-linked disorders in female individuals

A

female individuals will only express alleles or genes located on the active X-chromosome, thus the extent to which heterozygous female carriers of X-linked recessive disorders express phenotypic characteristics of the disease depends on the genetic inactivation pattern of the mutant versus the normal X-chromosome

leads to phenotypic variation among heterozygous female carriers of X-linked disorders (e.g., one female carrier of an X-linked disorder may be completely asymptomatic, while another has severe manifestations of the involved disease).

in female individuals who are homozygous for an X-linked recessive disorder, it does not matter which chromosome is inactivated

119
Q

genomic imprinting definition

A

a mechanism of gene regulation in which one allele of a gene is silenced and imprinted while the other allele is expressed depending on which parent it was inherited from (i.e., parent-of-origin effect)

must uphold the four principles of epigenetic imprinting

120
Q

four principles of epigenetic imprinting

A
  1. The product of gene transcription must be affected.
  2. The imprinting must be heritable in a somatic lineage.
  3. The process of genomic imprinting is initiated during gametogenesis.
  4. The imprint must be eliminated in the germline for sex-specific reprogramming to occur in the next generation of gametes

[effective, heritable (in somatic), has genesis in gametogenesis, and is eventually eliminated (in germline)]

121
Q

genomic imprinting mechanism

A

DNA methylation results, depending on the gene, in epigenetic silencing of either maternal or paternal chromosomes (e.g., if the paternal gene is silenced, only the maternal gene is expressed)

this then results in differentially methylated regions (DMRs)

122
Q

Angelman syndrome symptoms

A

an example of a genomic imprinting disorder

causes delayed development, problems with speech and balance, intellectual disability, and, sometimes, seizures. People with Angelman syndrome often smile and laugh frequently, and have happy, excitable personalities

[ANGEL: Usually angels fly so they can’t walk (Ataxia), but these angels lack wings, so they flap their hands to fly; Angels speak in tongues (Speech impairment), and angels don’t cry (excitable/happy mood)
MANS: M: Microcephaly, A: Attention span short, N: Neurodevelopmental disorder, S: Seizures]

123
Q

differentially methylated regions (DMRs)

A

the essential imprinting control regions, often exist within gene promoters, that are responsible for allelic expression

124
Q

pedigree chart

A

depicts a group’s genetic history in a family tree

Circles - Females
Squares - Males

125
Q

zygoten

A

stage of prophase I (meiosis) during which synapsis or syndesis (the pairing of homologous chromosomes) occurs and the formation of the synaptonemal complex also occurs

[zyg = syn]

126
Q

synapsis/syndesis

A

the pairing of homologous chromosomes during prophase I (zygotene specifically)]

[syn - same, desis - to bind, tie, fasten; bind together the same chromosomes]

127
Q

pachytene

A

stage of prophase I (meiosis) during which crossing over occurs; the chromatids crossover (form chiasmata) and exchange genetic material, resulting in genetic recombination of homologous chromosomes

(the chromatids re-pach their genetic material with one another]

128
Q

diplotene

A

stage of prophase I (meiosis) during which the synaptonemal complex disappears, then homologous chromosomes begin to separate (undoes synapsis/syndesis)) but the chromosomes remain held together by the chiasmata (crossover site)

129
Q

diakinesis

A

stage of prophase I (meiosis) during which the nuclear membrane disintegrates and the spindle apparatus begins to form

[movement (kinesis) between (dia) the end of prophase and beginning of metaphase]

130
Q

chiasmata

A

the crossover sites of chromatids during prophase I (meiosis)

131
Q

Angelman syndrome main causes

A

normally, only the maternal copy of the UBE3A [you (U) be (B) an ethereal (E3) angel (A) ma!] gene is active in the brain, but most cases of Angelman syndrome occur when part of the maternal copy is missing or damaged

in a few cases, Angelman syndrome is caused when two paternal copies of the gene are inherited, instead of one from each parent

132
Q

Prader-Willi syndrome symptoms

A

an example of a genomic imprinting disorder

characterized by behavior problems, intellectual disability, and short stature; hormonal symptoms include delayed puberty and wanting to eat constantly because they never feel full (hyperphagia) leading to obesity

[Weight Increased, Learning disabilities, Low muscle tone, Infertility (Due to hypogonadism), Short stature;WILLIS]

133
Q

Prader-Willi syndrome main cause

A

usually caused by deletion of a part of chromosome 15 passed down by the father

[Pappas Region Absent or Deleted ERroneously; PRADER]

134
Q

preanalytical phase

A

encompasses the selection of relevant diagnostic tests and the collection and transport of samples

specificity and sensitivity are important factors that should be considered when selecting a diagnostic test

135
Q

commonly analyzed biofluids

A

blood

urine

cerebrospinal fluid

fluid collection from punctures (e.g., ascites, pleural effusion)

136
Q

interference factors

A

affect sample quality

can be errors during sample collection (e.g., prolonged venous stasis during blood collection -> falsely elevated levels of K+ and Ca+)

can be errors during sample transport, such as:
exposure to strong light (e.g., leading to degradation of bilirubin -> in falsely low levels)
shaking of blood samples -> hemolysis

137
Q

qualitative methods during the analytical phase

A

the result is either positive or negative

E.g. pregnancy test, rapid antigen detection test, urine dipstick

138
Q

analytical phase

A

comprises sample processing and the generation of results

139
Q

quantitative methods

A

the concentration of a substance is determined

E.g. immunochemistry (e.g., ELISA for the detection of PSA), photometry (e.g., indirect determination of glucose concentration), and microscopy (e.g., manual blood cell count with differential)

140
Q

most important steps of the post-analytical phase

A
  1. Ensuring the correct allocation of results to patient data
  2. Plausibility check
  3. Conveyance of results
  4. Medical interpretation based on the combination of test results, patient history, and physical examination findings
141
Q

blotting definition

A

a technique used to detect DNA, RNA, and proteins that involves transferring the DNA, RNA, or proteins onto a membrane, and then the sample of interest is visualized using marked detector molecules (e.g., radiolabeled DNA or chemiluminescent detector RNA)

142
Q

most common blotting techniques employed in laboratory medicine

A

southern blot

western blot

northern blot

143
Q

the similar process all blotting techniques follow

A
  1. DNA, RNA, or protein molecules contained in the sample are separated by gel electrophoresis and/or electric charge, depending on their size (small molecules travel faster than bigger molecules).
  2. The separated molecules are transferred from the gel onto a membrane.
  3. The DNA, RNA, or protein molecule of interest is detected by using labeled, highly specific oligonucleotide probes, antibodies, or x-rays
144
Q

sample types of each blot method

A

northern - RNA

southern - DNA

western - proteins

[SNoW flakes DRoP; Southern blot, Northern blot, and Western blot are used on DNA, RNA, and Proteins respectively]

145
Q

northern blot principle of detection

A

annealing of radiolabeled or chemiluminescent detector RNA or DNA

146
Q

assessment of gene expression by measuring mRNA levels (e.g., expression of the FMR1 gene in different tissues in fragile X syndrome)

A

northern blot use

147
Q

southern blot detection

A

annealing of radiolabeled or chemiluminescent detector RNA or DNA

148
Q

detection of specific genes and nucleotide sequences, such as restriction fragment length polymorphisms (RFLPs) or minisatellite DNA and microsatellite DNA (called “variable number of tandem repeats,” VNTRs)

A

southern blot use

149
Q

western blot detection

A

direct or indirect detection using monoclonal antibodies (immunoglobulins that bind to a single, specific antigen)

150
Q

western blot use

A

measuring the amount of antigens and antibodies, confirmation of the presence of a protein in a sample, and rough estimation of its amount

151
Q

northern blot procedure

A

the RNA sample is cleaved by enzymes and separated by gel electrophoresis (commonly on agarose gels), then the separated and cleaved RNA is transferred (blotted) to a membrane

the membrane is incubated with labeled probes of RNA or DNA, and labeled probes recognize and anneal to the complementary strand if it is present on the membrane

152
Q

northern blot result

A

double-stranded RNA

one unlabeled strand (cleaved RNA sample)
one labeled strand that can be visualized using special techniques

153
Q

the two techniques for visualizing the one labeled strand produced with northern blot

A

when radiolabeled detector DNA/RNA is used, an x-ray film is placed against a western blot. This film develops when exposed to the label, creating dark regions that correspond to the target protein band.

in case of chemiluminescent DNA/RNA, a CCD camera that captures a digital image is used

154
Q

southern blot procedure

A

the DNA sample is cleaved by restriction enzymes and separated by gel electrophoresis, then the separated and cleaved DNA is transferred (blotted) to a filter membrane

the membrane is exposed to (radio)labeled oligonucleotides: DNA probes recognize and anneal to the complementary strand if it is present on the membrane

155
Q

southern blot results

A

double-stranded DNA

one unlabeled strand (cleaved DNA sample), and one labeled strand that can be visualized when the membrane is exposed to x-ray film

156
Q

western blot procedure

A

the protein sample is separated by gel electrophoresis, and the separated proteins are then transferred (blotted) to a membrane

the protein of interest is detected by a specific antibody that can be labeled directly or detected by a secondary, radiolabeled antibody

157
Q

southwestern blot sample

A

DNA-binding proteins

158
Q

southwestern blot principle of detection

A

target proteins binding to radiolabeled double-stranded DNA probes

159
Q

southwestern blot procedure

A

proteins are separated by gel electrophoresis and then blotted onto a nitrocellulose membrane (similar to western blot)

target proteins bind the radiolabeled double-stranded DNA probes (similar to southern blot)

160
Q

study of DNA-binding proteins, such as transcription factors (e.g. c-Fos, c-Jun)

A

southwestern blot uses

161
Q

enzyme-linked immunosorbent assay (ELISA)

A

an enzyme immunoassay that employs enzyme-labeled immunoreactants and an immunoadsorbent to determine the presence and concentration of certain proteins (e.g., tumor markers, viral proteins, drugs, antibodies) in serum

based on the highly specific immunologic interaction between an antibody and its antigen (i.e., the protein of interest) (but the specificity of ELISA is lower compared to western blot)

162
Q

two main types and the indirect type of ELISA and their functions

A

direct ELISA: tests for the antigen directly

indirect ELISA: tests for the antibody, which indicates the presence of an antigen (indirectly)

sandwich ELISA: an indirect ELISA that employs two antibodies that bind to different epitopes on the antigen of interest

163
Q

ELISA basic steps

A
  1. The antigen is fixed on a microtiter plate and bound by an enzyme-coupled antibody
  2. The enzyme catalyzes a reaction when incubated with its substrate which is chromogenic, chemifluorescent, or chemiluminescent
  3. The intensity of the signal is directly proportional to the amount of captured antigen
164
Q

direct ELISA steps

A
  1. The patient’s sample which supposedly contains the protein of interest (i.e., the antigen) is added to a well of microtiter plates with a buffered solution
  2. The specific antibody-enzyme conjugate is added to the solution
  3. A substrate for the enzyme is added
  4. Spectrometry is used to detect the generated chromophore
    Higher concentration of antibodies binding to the antigen → stronger signal
    Lower concentration of antibodies binding to the antigen → weaker signal
165
Q

direct ELISA function

A

tests for the antigen directly

166
Q

indirect ELISA function

A

tests for the antibody, which indicates the presence of an antigen (indirectly)

167
Q

sandwich ELISA function

A

an indirect ELISA that employs two antibodies that bind to different epitopes on the antigen of interest

168
Q

indirect ELISA steps

A
  1. The patient’s sample which supposedly contains the protein of interest (i.e., the antigen) is added to a well of microtiter plates with a buffered solution
  2. The primary antibody (name is different from direct ELISA) conjugate is added to the solution
  3. A substrate for the enzyme is added
  4. The primary antibody is detected by a secondary, labeled antibody
169
Q

sandwich ELISA steps

A
  1. A surface plate is coated with capture antibodies (not the patient’s antibodies)
  2. The sample is added to the coated plate where the captured antibodies bind the antigen of interest
  3. Specific (labeled) antibodies for the antigen are added; if the antigen is present, the antibody binds to the antigen
  4. A substrate for the enzyme is added (color, fluorescent, or electrochemical changes are due to the reaction between substrates and enzymes)
  5. Spectrometry, fluorescence, or electrochemical studies are performed to assess for the amount of antigens present
170
Q

Screening for HIV antibodies (high sensitivity, low specificity)

A

ELISA use

Testing for West Nile virus antibodies

Detection of the following organisms:
o	Mycobacterium tuberculosis
o	Rotavirus (in feces)
o	Hepatitis B virus
o	E. coli enterotoxin (in feces)

Detection of PSA

171
Q

polymerase chain reaction (PCR) overview

A

a technique that allows amplification of specific chromosome segments by producing more than a billion copies; this makes testing of very small sequences of DNA that could not otherwise be studied possible

172
Q

common sequences of DNA studied by PCR

A

mutations

microsatellite instability sequences

short tandem repeats (STRs)

173
Q

PCR procedure overview

A

PCR usually consists of 25–50 cycles, which are divided into three phases:

denaturation
hybridization
elongation and amplification

174
Q

denaturation PCR step

A

the sample is heated at a target temperature of 90–98°C (194–208°F) for 20–30 seconds as high temperatures break the hydrogen bonds between complementary base pairs of the double-stranded DNA and produce two single DNA strands.

175
Q

hybridization PCR step

A

the sample is cooled at a target temperature of 50–65°C (122–149°F) for 20–40 seconds, and then the following is added to the sample:
 Complementary DNA primers that are necessary for annealing
 Enzymes (for DNA synthesis): heat-stable DNA polymerase (Taq DNA polymerase)
 Deoxyribonucleotides (dNTPs)

primers bind the 3′ ends of the DNA sequence that needs to be amplified

176
Q

elongation and amplification PCR step

A

the sample is heated at a target temperature of 70–80°C (158–176°F); 72°C (162°F) is most commonly used for DNA polymerase

DNA polymerase uses dNTPs to elongate the primers, thereby replicating the sequence of the sample DNA strands

The process is repeated until it yields an amplification to 106 –1010 copies of the original DNA fragment (approximately 25–50 cycles)

177
Q

detection of HIV (particularly when ELISA and western blot are inconclusive)

A

PCR use

178
Q

reverse transcription polymerase chain reaction (RT-PCR) procedure

A
  1. A sample mRNA is converted to complementary DNA (cDNA) by reverse transcriptase
  2. cDNA is amplified by the standard PCR procedure (see above)
179
Q

reverse transcription polymerase chain reaction (RT-PCR) use

A

detection and quantification of mRNA levels in a sample

180
Q

real-time polymerase chain reaction procedure

A

also known as quantitative PCR or qPCR

a PCR technique that utilizes fluorescence (e.g., intercalating dyes or DNA probes) for monitoring the amplification of targeted DNA during the PCR via computer software (in a graph)

melting temperatures specific to the amplified fragment allow for high specificity.

there are many types, including quantitative reverse transcription PCR (RT-qPCR) and semiquantitative real-time PCR

181
Q

real-time polymerase chain reaction uses

A

allows monitoring of a targeted product at any point throughout the amplification

rapidly detect nucleic acids for diagnosis (e.g., RT-qPCR for SARS-CoV2)

easily quantify gene expression (e.g., via comparing to a standard curve of serial dilutions)

quantify and genotype viruses

182
Q

chromosome testing purposes

A

used in the (prenatal) diagnosis of inherited disorders, e.g. to detect gene mutations

used in the diagnosis of infectious diseases (e.g., diphtheria)

used in forensics

used in tumor diagnostics

183
Q

genetic markers

A

individual differences in the DNA sequence of a specific region of the genome

(repetitive sequences of various lengths which are present in several noncoding regions of the genome and which differ in sequence motif length

since the frequency of repetition differs in each individual, polymorphisms in DNA form the basis for the diagnosis of diseases and allow individuals to be identified)

184
Q

three different markers for DNA analysis

A

microsatellites (short tandem repeats, STRs)

SNPs (single nucleotide polymorphism)

RFLP (restriction fragment length polymorphism)

185
Q

microsatellites

A

AKA short tandem repeats (STRs); belong to the VNTRs (variable number tandem repeats)

repetitive sequences of several base pairs in DNA that are highly polymorphic

can be analyzed via PCR to identify individuals (very small amounts of DNA suffice for analysis)

186
Q

VNTRs

A

variable number tandem repeats; short nucleotide sequences in the genome of an individual that are repeated a variable number of times

187
Q

SNPs

A

single nucleotide polymorphism

DNA sequence variants in a population that differ by only a single base pair; usually caused by errors during DNA replication and are point mutations

188
Q

RFLP

A

restriction fragment length polymorphism

depending on the DNA sequence of an individual, cleaving of chromosomal DNA with restriction enzymes leads to DNA fragments of variable lengths

189
Q

RFLP detection method

A

the DNA fragments of variable lengths s/p cleaving of chromosomal DNA with restriction enzymes are analyzed using Southern blot and detected by probes

190
Q

genetic fingerprint

A

the DNA profile of an individual, especially as determined by microsatellite analysis

191
Q

DNA diagnostics uses

A

suitable for the direct or indirect detection of a gene mutation that results in disease

can also be used to exclude the presence of a gene mutation

192
Q

direct detection prerequisites

A

the causal gene for the (suspected) disease is known

193
Q

restriction endonucleases

A

AKA restriction enzymes

enzymes that cleave double-stranded DNA at an enzyme-specific nucleotide sequence

194
Q

direct detection process

A

amplification of a specific region of the affected gene using PCR

detection of a mutation, e.g., through sequencing or cleavage of DNA fragments using restriction enzymes

analysis via gel electrophoresis: detection is based on the altered mobility of the DNA fragments of mutated and normal alleles in gel electrophoresis

195
Q

restriction site cleavage

A

most restriction sites are palindromes

cleaved by restriction enzymes (restriction endonucleases)

cleavage of DNA using restriction enzymes results in sticky ends or blunt ends.

196
Q

origin of restriction enzymes

A

prokaryotic defense system against foreign DNA

197
Q

genetic linkage analysis

A

AKA indirect detection

analysis of genetic markers associated with the mutated gene and comparison of the patient’s genotype with that of unaffected family members

performed if direct detection is not possible

198
Q

indirect detection prerequisite

A

the disease occurs in several family members and the suspected locus is known

199
Q

indirect detection result

A

there is no direct detection of a gene mutation, but a probability of the presence of a certain mutation that causes disease (genetic risk score) can be calculated

the validity of indirect DNA diagnostics depends on the pattern of inheritance and the number of family members being investigated

200
Q

karyotyping overview

A

can be used to visualize chromosomes for examining chromosome numbers and for an overview of potential structural changes within a chromosome

determines the number, size, morphology, banding pattern, and the arm-length ratio of chromosomes

helpful for the diagnosis of trisomies, monosomies, and sex chromosome disorders

201
Q

banding pattern definition

A

transverse bands of various widths and distribution, which can be induced depending on the preparation and staining technique

202
Q

banding pattern preparation

A

the cell sample is cultivated and cell division is stimulated.

to obtain chromosomes during metaphase, the cells are arrested using the spindle inhibitor colchicine

203
Q

colchicine

A

interferes with the formation of the microtubules of the mitotic spindle, leaving the cell suspended in metaphase and arresting mitosis

204
Q

banding techniques

A

staining with quinacrine (fluorescent bands; not used routinely in diagnostics)

Giemsa banding (standard banding technique, results in dark G bands with transcriptionally inactive chromatin and bright, transcriptionally active R bands)

205
Q

banding pattern analysis

A

assessment of an average 10–15 metaphase chromosome pairs in 1250x magnification

206
Q

staining with quinacrine

A

fluorescent bands; not used routinely in diagnostics

207
Q

Giemsa banding

A

standard banding technique; results in dark G bands with transcriptionally inactive chromatin and bright, transcriptionally active R bands

208
Q

karyotype overview

A

evaluation of a karyogram according to the number and the structure (morphology, length, arm-ratio, pattern of banding, size) of the chromosomes

the total number of chromosomes is stated first followed by the type of sex chromosome present (e.g., 46, XX = healthy, female karyotype)

anomalies, if present, are mentioned last (e.g., 47, XY+21: male karyotype with trisomy 21).

209
Q

FISH overview

A

fluorescence in situ hybridization

a method used for the staining of specific DNA sequences by a fluorescence-labeled DNA or RNA probe

E.g., to stain chromosomes in karyograms, in tumor diagnosis, or to map specific genes on chromosomes in metaphase

210
Q

FISH procedure

A

denaturation of DNA in the prepared chromosomes

hybridization of the DNA with a single-stranded, fluorescence-labeled DNA probe that is complementary to a specific DNA sequence

analysis of the chromosome set in fluorescence microscopy (fluorescent signal indicates the site of the bound probe)

211
Q

microdeletion in FISH

A

the deleted region does not exhibit fluorescence, compared to the region present in the same locus of the other copy of the chromosome

212
Q

translocation in FISH

A

fluorescence signal from one chromosome is present in a different chromosome

213
Q

duplication in FISH

A

extra copies of chromosomes that exhibit fluorescence in addition to the normal ones

214
Q

phytohemagglutinin

A

a mitogen that increases the proliferation of peripheral blood lymphocytes

215
Q

FISH result

A

the specific staining increases the resolution compared to the classical staining methods of karyograms, thus even minor chromosomal aberrations (e.g., microdeletions) can be identified.

FISH is also possible on chromosomes in interphase

216
Q

FISH uses

A

direct visualization of chromosomal anomalies at specific gene loci on a molecular level

detection of microdeletions (2–3 × 106 base pairs) such as in DiGeorge syndrome

search for evidence of a Philadelphia chromosome translocation t(9;22)

217
Q

array comparative genome hybridization (CGH)

A

another name for DNA microarray

218
Q

DNA microarray

A

mainly used to simultaneously examine expression levels of multiple genes or to genotype many regions at the same time

219
Q

DNA microarray prepartaion of the sample

A

the first step in microarray procedure

a sample (m)RNA and control (m)RNA are converted to complementary DNA (cDNA) by reverse transcriptase

cDNA is then labeled with a fluorescent dye, one color for the sample that is being tested, another color for the control (e.g., green for the control, red for the sample being tested)

mRNA is removed and samples are combined.

220
Q

DNA microarray preparation of the chip

A

the second step in microarray procedure

thousands of genetic sequences of nucleic acid (DNA or RNA) probes are attached to a chip (e.g., glass, silicon).

oth patient and control DNA is applied to this chip and hybridizes to the probes on the chip, which is mounted to a scanner that can detect complementary binding of probes and sample sequences

each region of the chip stands for a known genetic sequence, and the higher the expression of the gene in one sample, the more intense the fluorescence.

221
Q

DNA microarray uses

A

helpful for the detection of copy number variations (CNVs) and sequencing

222
Q

DNA microarray sequencing

A

determination of the exact sequence of base pairs of a gene; e.g., to demonstrate an unknown mutation on a disease-causing gene

223
Q

copy number variations (CNVs)

A

single nucleotide polymorphisms (SNPs) that are used for genotyping, forensic science, cancer mutations, genetic linkage analysis, and genetic testing

224
Q

CRISPR gene editing

A

a technique in genetic engineering that employs the prokaryote CRISPR/Cas9 defense system directed against foreign gene sequences to modify the genomes of living organisms (e.g., adding or deleting genes in DNA sequences)

225
Q

CRISPR

A

clustered regularly interspaced short palindromic repeats; a family of DNA sequences of prokaryotic origin

226
Q

crRNA

A

CRISPR RNA

transcribed CRISPR sequence; binds to Cas9

227
Q

Cas9

A

CRISPR-associated system 9

endonuclease that produces single or double-strand breaks at a specific nucleotide sequence guided by a site-specific RNA (targeted DNA double-strand break)

228
Q

tracrRNA

A

transactivating crRNA

RNA sequence that is partially complementary to crRNA; also binds to Cas9 (needed for Cas9 maturation)

229
Q

Cas9 in prokaryotes

A

the guide RNA consists of crRNA and tracrRNA

230
Q

Cas9 for laboratory use

A

a single guide RNA is specifically designed and synthesized

231
Q

cas9 gene sequence location

A

found adjacent to the CRISPR sequence

232
Q

adaptive prokaryotic immune response

A
  1. Foreign DNA is incorporated into own DNA at the CRISPR locus (acquisition)
  2. The CRISPR locus is transcribed together with foreign DNA and forms the primary transcript.
  3. The primary transcript binds tracrRNA and is processed to form a crRNA-tracrRNA hybrid, which contains a foreign genetic sequence
  4. crRNA-tracrRNA hybrid forms a complex with Cas9.
  5. Now foreign DNA that contains the sequence complementary to the one contained by the crRNA/tracrRNA/Cas9 complex can be recognized and cleaved
233
Q

CRISPR/Cas9 in gene editing

A

for gene editing purposes, tracrRNA and crRNA are combined into one molecule, the single synthetic guide RNA (sgRNA) that is complementary to the DNA sequence of interest (target DNA)

234
Q

three major variants of Cas9 used in CRISPR gene editing

A

wild-type Cas9

Cas9D10A

nuclease-deficient Cas9

235
Q

wild-type Cas9

A

major variant of Cas9 used in CRISPR gene editing; cleaves dsDNA

can repair induced dsDNA breaks through nonhomologous end joining (NHEJ) pathway or homology-directed repair (HDR) pathway

236
Q

nonhomologous end joining (NHEJ) pathway

A

pathway for wild-type Cas9 to repair dsDNA

deletion of the targeted gene (gene knock-out) → accidental frameshift mutations

237
Q

homology-directed repair (HDR) pathway

A

pathway for wild-type Cas9 to repair dsDNA

insertion of donor DNA (gene knock-in) → mutation in the gene of interest

238
Q

Cas9D10A

A

major variant of Cas9 used in CRISPR gene editing; cleaves only one DNA strand (nickase activity)

more specific than wild-type Cas9 because it does not activate NHEJ (nonhomologous end joining) but only the high-fidelity HDR (homology-directed repair) pathway

239
Q

nuclease-deficient Cas9

A

major variant of Cas9 used in CRISPR gene editing; mutations in nuclease domains prevent cleavage but not binding

can be used to activate or silence genes by creating fusion proteins of Cas9 with effector proteins

240
Q

potential applications of CRISPR/Cas9

A

immuno-oncology (i.e. using manipulated immune cells to fight cancer)

curing genetic diseases by replacing the alleles of genes associated with disease phenotypes with unaffected variants

eliminating virulence factors of pathogens

241
Q

hemoglobin electrophoresis definition

A

a screening test that detects and quantifies the types of hemoglobins present in a sample by separating them based on their electrical charge

242
Q

hemoglobin electrophoresis applications

A

diagnostic work-up of hemolytic anemias

screening for or evaluation of hemoglobinopathies in high-risk individuals (e.g., positive family history)

evaluation of abnormal erythrocytes on peripheral blood smear

243
Q

hemoglobin electrophoresis procedure

A

a sample of the patient’s hemoglobin is obtained by hemolyzing a sample of blood using a hemolysate reagent and the sample is added to the gel electrophoresis buffer

an electric field is applied to the buffer that causes the different hemoglobin types to separate according to their electrical charge; hemoglobin is negatively charged at an alkaline pH and migrates on the gel towards the anode, forming a band with the degree of negative charge of the hemoglobin molecule determining the migration speed and distance from the cathode to the anode

a stain is applied to the gel to make the charged molecules visible

244
Q

hemoglobin electrophoresis speeds

A

HbA migrates the fastest and therefore the greatest distance, followed by Hb F, Hb S, and Hb A2, and Hb C (A > F > S > A2 and C)

[A FaSt TouCan can go far (A > F > S > A2 > C)]

245
Q

hemoglobin C migration during electrophoresis

A

HbC migrates the least because a missense mutation replaces the negatively charged glutamic acid with the positively charged lysine

246
Q

hemoglobin S migration during electrophoresis

A

migrates less than HbA because of the replacement of the negatively charged glutamic acid with the neutral valine

247
Q

expected hemoglobin electrophoresis finding for normal adult

A

wide HbA band (AA)

248
Q

expected hemoglobin electrophoresis finding for normal fetus

A

HbA and widened HbF band (AF)

249
Q

expected hemoglobin electrophoresis finding for beta thalassemia minor (trait)

A

narrowed HbA band and widened HbA2 band

250
Q

expected hemoglobin electrophoresis finding for beta thalassemia major

A

no HbA band; widened HbA2 and HbF bands

251
Q

expected hemoglobin electrophoresis finding for sickle cell trait

A

HbA and HbS bands (AS)

252
Q

expected hemoglobin electrophoresis finding for sickle cell anemia

A

no HbA band; wide HbS band (SS)

253
Q

expected hemoglobin electrophoresis finding for HbC trait

A

HbA and HbC bands (AC)

254
Q

expected hemoglobin electrophoresis finding for HbC disease

A

no HbA band; wide HbC band (CC)

255
Q

expected hemoglobin electrophoresis finding for HbSC disease

A

no HbA band; HbS and HbC bands (SC)

256
Q

RNA interference definition

A

inhibition of gene expression via small, non-coding RNA molecules that bind target RNA (mostly mRNA)

257
Q

RNA interference functions

A

inhibition of gene expression

defense mechanism against foreign RNA molecules

258
Q

RNA interference mechanisms

A

inhibition of translation

mRNA destabilization via removal of poly(A) tail at the 3′OH-end of target mRNA (deadenylation) and decapping

mRNA degradation

259
Q

Cre-Lox system

A

used to induce recombination between specific DNA sites (e.g., to study the effect of gene insertions or deletions)

consists of Cre recombinase and LoxP sequences

260
Q

Cre recombinase

A

an enzyme that catalyzes recombination between LoxP sequences

261
Q

LoxP sequences

A

short DNA sequences within the cell genome that have sites for Cre recombinase binding

262
Q

molecular cloning definition

A

experimental production of recombinant DNA molecules within host organisms (e.g., bacterial hosts)

263
Q

molecular cloning process

A
  1. Isolation of eukaryotic target mRNA
  2. Production of complementary DNA (cDNA) using reverse transcriptase
  3. Insertion of cDNA fragments into a cloning vector (e.g., bacterial plasmids carrying the antibiotic resistance genes)
  4. Transformation of the produced recombinant plasmid into bacteria
  5. Selection of bacteria that contains the plasmid (e.g., via antibiotic exposure when cloning antibiotic resistance genes)
264
Q

molecular cloning result

A

synthesis of multiple copies of target cDNA (cloned DNA)

265
Q

assessment of RNA splicing (including splicing errors)

A

northern blot use

266
Q

southern blot use examples

A

restriction fragment length polymorphisms (RFLPs)

minisatellite DNA and microsatellite DNA (called “variable number of tandem repeats,” VNTRs)

267
Q

testing for West Nile virus antibodies

A

ELISA use

268
Q

detection of Mycobacterium tuberculosis

A

ELISA use

269
Q

detection of Rotavirus (in feces)

A

ELISA use

270
Q

detection of Hepatitis B virus

A

ELISA use

271
Q

detection of E. coli enterotoxin (in feces)

A

ELISA use

272
Q

detection of PSA

A

ELISA use

273
Q

method useful for the detection of neonatal exposure to HIV

A

PCR use

274
Q

PCR use benefits

A

positive early after infection and is not affected by the immune status of the patient (e.g., immunocompromised patients may not produce an antibody response)

275
Q

diagnosis of bacterial and viral infections (e.g., Lyme disease, HSV encephalitis)

A

PCR use

276
Q

diagnosis of immunodeficiency (e.g., severe combined immunodeficiency)

A

PCR use

277
Q

forensic analysis (e.g., comparison of DNA samples from suspects, paternity testing)

A

PCR use

278
Q

sequencing of mutations

A

PCR use

Intro Classes (13 decks)

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