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Foundations 1 > Genetics: Genome, Chromosomes, Pedigrees, Abnormalities > Flashcards

Genetics: Genome, Chromosomes, Pedigrees, Abnormalities Flashcards

1
Q

How many chromosomes do humans have?

A

22 pairs of autosomes, 2 sex chromosomes (XX or XY)

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2
Q

(T/F) Chromosome number is the same between all mammals

A

False

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3
Q

Genotype

A

Genetic composition of an individual; alleles at a specific genetic locus

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4
Q

Phenotype

A

Observable expression of a particular gene(s)

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5
Q

Penetrance

A

Frequency with which a genotype manifests itself in a given phenotype

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6
Q

Relationship of genotype, phenotype, and penetrance

A

Phenotype is the result of a combination of penetrance and genotype

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7
Q

Chromosomes are condensed in…

A

Metaphase

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8
Q

Metacentric

A

Centromere in middle of chromosome

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9
Q

Acrocentric

A

Only a small amount of repetitive DNA above centromere

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10
Q

Submetacentric

A

Short p arms above centromere

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11
Q

Karyotype

A

Number and appearance of complete set of chromosomes in nucleus of eukaryotic cell

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12
Q

G-Banding

A

Technique to produce visible karyotype by staining condensed chromosomes

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13
Q

Euchromatin

A

Light-staining, early-replicating, transcribed/translated DNA segments

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14
Q

Heterochromatin

A

Dark-staining, late-replicating DNA segments that remain condensed. Includes centromeres, inactive loci, and inactive X chromosome

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15
Q

Locus

A

Specific position on a chromosome

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16
Q

Allele

A

Alternative forms of a gene or DNA sequence at a given locus. Ex. A, a, B, b

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17
Q

Homozygous

A

Both alleles are identical. Ex. AA, aa

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18
Q

Heterozygous

A

Different alleles on each chromosome. Ex. Aa, Bb

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19
Q

Compound Heterozygous

A

2 different mutant (recessive) alleles at a given locus. Ex. a1a2, Cystic Fibrosis

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20
Q

Double Heterozygous

A

One mutant allele at each of 2 different loci. Ex. ab or bc; associated with deafness.

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21
Q

Main source of genetic diversity

A

Recombination

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22
Q

Recombination occurs during…

A

Meiosis 1

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23
Q

Physical distances

A

Base pairs, kilobases, Megabases, etc.

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24
Q

Base pairs in human genome

A

3x10^9

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25
Q

Genetic distances

A

Centimorgans (cM). 1 cM = 1/100 meiosis will have a recombination.

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26
Q

Genetic mapping

A

Creating a map by assigning DNA fragments to chromosomes. Based on recombination/meiotic segregation, genetic techniques such as pedigree analysis or breeding experiments

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27
Q

Synteny

A

Physical co-localization of genetic loci on the same chromosome within an individual or species

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28
Q

Linkage

A

< 50% cM, lower than expected recombination frequency between two loci

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29
Q

Haplotype

A

Series of alleles found at linked loci on a single chromosome

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30
Q

Physical mapping

A

Mapping genes or DNA sequences on a chromosome that does not rely on meiotic segregation/recombination

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31
Q

Polymorphism

A

Existence of 2 or more phenotypic variants at significant frequencies in the population. Used as a tool for genetic mapping and testing (diseases, crime, paternity). Underlies genetic diversity, basis for phenotype variability and individual responses to drugs.

32
Q

Genetic marker

A

A polymorphic DNA or protein sequence deriving from a single known chromosomal location. Can be used to identify individuals or species. Includes RFLPs, microsatellites/VNTRs, SNPs.

33
Q

RFLP

A

A polymorphic difference in the size of allelic restriction fragments between homologous DNA mlcls as a result of the polymorphic presence or absence of a particular restriction site. A genetic marker.

34
Q

Microsatellites/VNTRs

A

A genetic marker with many alleles that is highly informative. Can be typed by automated multiplex PCR; easy physical localization, distributed throughout genome.

35
Q

SNPs

A

A genetic marker that can be types on a very large scale by automated equipment without gel electrophoresis.

Less informative than microsatellites, but may have future use in predicting disease susceptibility, drug responsiveness, “personalized medicine,” understanding genetic contributions to complex diseases.

36
Q

% of human genome that codes for proteins

A

1.3%, < 30,000 genes

37
Q

(T/F) mRNA contains introns and exons

A

False, only exons

38
Q

Exons encode…

A

5’-untranslated regions, protein coding sequence/open reading frame, and 3’-untranslated regions

39
Q

of exons and introns in human genes

A

1 - 178 total exons, avg 8.8 exons and 7.8 introns

40
Q

Average length of exon

A

145 bp

41
Q

Genomic DNA

A

Same for given individual in any tissue or developmental stage. Contains regulatory sequences (promoters, enhancers), introns, exons, repetitive sequences (40-45% of genome)

42
Q

cDNA

A

DNA synthesized from mRNA by reverse transcriptase and DNA polymerase. Different for each tissue and developmental stage in a given individual. Contains mature transcripts (5’-UTR, ORF, 3’UTR, polyA tail), no introns.

43
Q

“Mutant” allele =

A

Recessive allele

44
Q

(delta)F508 means…

A

Deletion of phenylalanine at amino acid number 508

45
Q

R1066C means…

A

Transition from arginine to cysteine at amino acid number 1066

46
Q

Consanguinity

A

“with blood,” indicates a couple that is related. Add 2 horizontal lines on pedigree.

47
Q

To receive info on miscarriages, still births, children no longer living from a patient, ask:

A

“How many pregnancies have you had?” instead of “How many children do you have?

48
Q

When taking family histories…

A

Obtain siblings’ histories first, then parental family history and medical histories. Doesn’t matter whether you choose paternal or maternal first. Should always have 3-generation family history at a minimum.

49
Q

Mendelian Diseases

A

Diseases that are the result of a single gene mutation

50
Q

Autosomal

A

Encoded on an autosome

51
Q

X-linked

A

Encoded on the X chromosome

52
Q

Dominant

A

Conditions expressed in heterozygotes

53
Q

Recessive

A

Conditions that are clinically manifest only in individuals homozygous for the mutant allele

54
Q

Punnett Square

A

Shows probability of progeny with each possible genotype resulting from 2 parents heterozygous for a mutation

55
Q

Autosomal dominant inheritance pattern

A

Affected individuals give rise to affected progeny, males transmit to both males and females

56
Q

Autosomal recessive inheritance pattern

A

Unaffected individuals give rise to affected progeny (homozygous recessive), both males and females affected, heterozygotes are carriers

57
Q

X-linked recessive inheritance pattern

A

Unaffected individuals give rise to affected progeny, typically only males affected (except for rare cases that result from mutations caused by X translocations, extremely skewed X inactivation of the wild type X in a female), can have female carriers.

58
Q

X-linked dominant inheritance pattern

A

Affected individuals give rise to affected progeny, males transmit only to female progeny

59
Q

Aneuploidy

A

Abnormal chromosome number, which is not an exact multiple of the haploid number (n = 23). Results from abnormal chromosome segregation during mitosis or meiosis (mostly female meiosis I and risk increases with advancing maternal age), lagging movement of chromosome or chromatin

60
Q

Nondisjunction

A

Failure of paired chromosomes to separate in anaphase of Meiosis I or failure of sister chromosomes to disjoin at Meiosis II or Mitosis

61
Q

Types of genetic mutations:

A

Aneuploidy, polyploidy, chromosomal rearrangements, single gene mutations, multifactorial disorders

62
Q

Types of aneuploidy

A

Trisomies (3 instances of a chromosome instead of 2, most embryonic or fetal lethal), monosomies (embryonic lethal), tetrasomies, etc.

63
Q

(T/F) Aneuploidy of sex chromosomes results in less severe phenotype than that of autosomes.

A

True

64
Q

Polyploidy

A

Any multiple of the haploid number of chromosomes (n = 23). Not compatible with survival, observed in small % of spontaneous abortions.

65
Q

Triploidy

A

Most common polyploidy (3n). Ex. 69XXX, 69XXY, 69XYY. Occurs in 1% of all conceptions, livebirths rare, caused by fertilization by 2 sperm, error in maternal meiosis II.

66
Q

Chromosomal rearrangement

A

Results from chromosome breakage or recombination between mispaired chromosomes during meiosis. 1/1000 infants born with symptomatic chromosomal rearrangement, non-symptomatic rearrangements often account for infertility/miscarriages.

67
Q

Types of chromosomal rearrangements

A

Deletions (loss of part of a chromosome, contiguous gene syndromes), translocations (part of chromosome is transferred to another, only causes disease when break is within important gene or copy # of gene is changed), inversions, formation of ring chromosomes

68
Q

Types of translocations

A

Balanced reciprocal translocation (equal size portions transferred, few symptoms but may have infertility. DNA not lost usually.), Robertsonian translocation (fusion of q arms of 2 acrocentric chromosomes, considered balanced since lost p arms contain only repetitive arrays of rRNA genes)

69
Q

46XX means…

A

Normal female

70
Q

46XYt(3;11) means…

A

Male with balanced translocation, chromosomes 3 and 11 abnormal about 75% of the time

71
Q

46XYder(14;21)

A

Male with Robertsonian translocation between chromosomes 14 and 21.

72
Q

Types of single gene mutations

A

Point mutations, deletions (large ones can lead to contiguous gene syndromes, can cause frameshift), insertions (can cause frameshift), mutations (in regulatory regions, <1% of disease causing mutations, can be silent or have minor effects on protein expression), mitochondrial mutations (maternal inheritance pattern)

73
Q

Point mutations

A

Change in single base pair, 60% of disease causing mutations

74
Q

Types of point mutations

A

Transition (purine replaced by another purine), transversion (purine to pyrimidine or v.v.), missense mutation (generates amino acid change), nonsense mutation (generates premature stop codon), synonymous or silent base change (no resulting amino acid change), splice site mutation (changes in intron-exon junction or intron branch site)

75
Q

Multifactorial disorders

A

Also called polygenic disease or complex diseases; caused by interacting genetic and environmental risk factors, not a single major mutation; encompasses most common diseases (diabetes, cardiovascular diseases, allergies, susceptibility to infection diseases)

76
Q

X inactivation

A

In females, one X chromosome is randomly inactivated - normally 50:50, very rarely 90:10.

77
Q

(T/F) Inactivating an autosome is not compatible with life.

A

True. Cannot inactivate autosome even if X chromosome was translocated onto it.

Foundations 1 (11 decks)

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