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Path Exam 2 > Genetics > Flashcards

Genetics Flashcards

1
Q

what happens to the mutations affecting germ cells?

A

can be transmitted to progeny

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2
Q

what happens to the mutations affecting somatic cells?

A

result in tumors or developmental malformations

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3
Q

what is a point mutation? example?

A

single nucleotide base substituted

sickle cell anemia

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4
Q

what is frameshift mutation

A

insertion or deletion of one or two base pairs, altering reading frame of the DNA strand

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5
Q

what is trinucleotide repeat mutations?

examples?

A

amplification of sequence of 3 nucleotides

fragile X syndrome

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6
Q

what is a single nucleotide polymorphism?
how many have been identified?
what is the significance of them?

A

variation in just one nucleotide at a single site on the DNA molecule
over 6 million have been identified but most are within exons, introns or intergenic regions
they may be markers for multigenic complex diseases, such as diabetes or hypertension

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7
Q

what are copy number variations?

A

different numbers of large contiguous stretches of DNA, from 1000 to millions of base pairs
about half involve gene coding sequences, and this may account for much phenotypic variation

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8
Q

what are epigenetic changes?

A

modulation of gene expression without altered DNA sequence
important in development and normal homeostasis.
methylation of promoter regions make them inaccessible to RNA polymerase, thus reducing protein synthesis

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9
Q

alterations in non-coding rnas

A

micro RNAs (miRNA) inhibit translation of their target messenger RNAs into their corresponding proteins

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10
Q

what are the types of genetic disorders?

A

disorders with multifactorial (polygenic) inheritance

cytogenetic disorders- chromosomal aberrations (autosomes and sex chromosomes)

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11
Q

what are autosomal dominant disorders?

A

altered gene locus is on an autosome and the disease will be evident clinically when only one of the chromosomes in the pair exhibits a mutation at the affected gene locus

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12
Q

characteristic of autosomal dominant disorders

A

majority of disorders create outward physical changes and many exhibit a delayed age of onset, even tho the mutant gene is present from birth
one of the parents is usually affected, and both males and females can have the disorder and transmit the mutant gene

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13
Q

what is reduced or incomplete penetrance?

A

person has a mutant gene but does not express it phenotypically

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14
Q

what is variable expressivity?

A

trait is seen phenotypically in the individuals having the mutant gene but is expressed differently among individuals

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15
Q

what is de novo mutation?

A

affected individuals may not have affected parents bc their disease arose from a new mutation

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16
Q

what is neurofibromatosis?

A

example of nearly 100% penetrance

but gene has variable expressivity among the affected individuals

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17
Q

autosomal recessive

A

age of onset is earlier in life
expression of the defect tends to be more uniform and complete penetrance is common
new mutations do occur but not usually detected bc individual would be a carrier without clinical manifestations
many of these disorders present with enzyme defects that produce inborn errors of metabolism
carriers may possess reduced amounts of the normal enzyme

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18
Q

what trait may be carried on y chromosome?

A

hairy ears

all sexlinked diseases are x-linked

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19
Q

x-linked recessive

A

rarely heterozygous females may demonstrate full expression due to unfavorable lyonization

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20
Q

lyonization

A

all but one x chromosome is randomly activated in all of the cells within zygote- barr body formation within 16 days of conception
either maternal or paternal x may be inactivated in each cell and that x remains inactivated in the progeny of the cell
in disorders of x chromosomes- typically females are an even mixture of normal and abnormal chromosomes
unfavorable lyonization refers to inactivation of an abnormally high percentage of normal x chromosomes- leading to clinical evidence of the disease in a heterozygote

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21
Q

x-linked dominant

A

heteroxygous, homozygous, hemizygous are affected

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22
Q

marfan syndrome

A

autosomal dominant disorder of connective tissue due to mutation of the FBN1 gene, resulting in abnormal fibrillin- glycoprotein necessary for normal elastic fiber production- change consistency of tissue, skin, joint- hyperflexible

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23
Q

what is the prevalence of marfan?

A

1 in 5000

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24
Q

clinical appearance of marfan?

A

tall, thin body habitus with abnormally long legs, arms and fingers- arachnodactyly- spider fingers
dislocation of lens of the eye
aortic aneurysm and dissection leading to heart failure and aortic rupture

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25
Q

ehlers-danlos syndrome

A

6 different types may exist in both dominant and recessive forms
problem of collagen synthesis and there are 30 diff types of collagen

26
Q

clinical appearance of ehlers-danlos?

A

hyperextensible skin and hypermobile joints
skn fragility and delayed wound healing
rupture of colon, larger arteries
hernia

27
Q

familial hypercholesterolemia

A

disease caused by mutation in receptor proteins
mutation in the gene for the LDL receptor (over 900 identified) results in impaired metabolism and increased LDL cholesterol in the plasma
causes xanthomas of the skin and premature atherosclerosis

28
Q

frequency of familial hypercholesterolemia

A

1 in 500 in the population

29
Q

effects of familial hypercholesterolemia

A

heterozygotes have 2-3x increased cholesterol levels
homozygotes have over 5x
homozygotes often die of MI before 15 years of age

30
Q

drugs for cholesterol levles

A

role of LDL receptorbs lef to design statin drugs to control cholesterol levels
recent approval of lomitapide to treat homozygous form

31
Q

what is cystic fibrosis

A

inherited problems with chlorine channels- develop very viscous mucoid secretions that will affect the lung
bronchiesctasis- dilations

32
Q

phenylketonuria

A

disease cause by mutation in enzyme proteins
autosomal recessive disorder
severe lack of phenylalanine hydroxylase- leading to hyperphenylalaninemia and PKU
affected infants are normal at birth, but elevated phenylalanine levels impair brain development, and mental retardation is evident by 6 months of age
screening of newborns for this condition is mandatory in the US
restriction of dietary phenylalanine intake will prevent the mental retardation

33
Q

rate of phenylketonuria

A

affects 1 in 10000 caucasian infants

34
Q

lysosomal storage diseases

A

autosomal recessive transmission
commonly affect infants and young children
accumulation of insoluble large molecules (sphingolipids and mucopolysaccharides) in macrophages and hepatosplenomegaly
frequent cns involvement, mental retardation and or early death

35
Q

examples of lysosomal storage diseases

A

tay-sachs
niemann-pick-single myelin
gaucher disease- glycolipids
mucopolysaccharidoses

36
Q

mucopolysaccharide storage diseases

A

most are autosomal recessive traits
due to lack of any one of the severa enzymes necessary to degrade mucopolysaccharides
affected patients have coarse facial features, clouding of cornea, joint stiffness and mental retardation
seven variants

37
Q

hurler disease

A

deficiency of alpha-l-iduronidase (laronidase)
life expectancy of 6-10 years untreated
bone marrow transplant or enzyme replacement may improve the outlook but not all aspects of the disease are corrected
cost of enzyme >300000 annually

38
Q

hunter syndrome

A

deficiency of l-iduronate sulfatase
x-linked inheritance pattern(males typically affected)
absence of corneal clouding and milder clinical course but otherwise similar to hurler syndrome

39
Q

disorders with multifactorial inheritance

A

many physiologic traits (height, weight, blood pressure, hair color)
may underlie common diseases such as diabetes, hypertension, gout, schizophrenia, bipolar disorder
two or more genes responsible, plus environmental, nongenetic influences
frequency of inheritance ranges from 2-7%

40
Q

what is karyotype?

A

composite picture o f human chromosome strands can be stained, photographed and arranged in pairs. each chromosome set can be seen to possess distinctive pattern of alternating light and dark bands of variable widths

41
Q

normal karyotupe

A

23 pairs of chromosome
22 pairs of autosome and 1 pair of sex chromosomes
normal chromosome count is 46

42
Q

what number of newborns have chromosomal abnormality?

what percent of 1st trimester spontaneous abortions of fetus have a chromosomal abnormality?

A

1 in 200

50%

43
Q

euploid

A

normal chromosomal count

46

44
Q

polyploidy

A

increased chromosome count that is a multiple of that normally seen

45
Q

aneuploidy

A

any number that is not an exact multiple of the normal chromosome count

46
Q

trisomy

A

extra chromosome

47
Q

monosomy

A

absence of a chromosome

48
Q

structural abnormalities

A

result from chromosome breakage followed by loss or rearrangement of material

49
Q

translocation

A

transfer of one part of one chromosome to another nonhomologous chromosome
fragments are exchanged between two chromosomes- reciprocal translocation

50
Q

deletion

A

loss of a portion of a chromosome

51
Q

inversion

A

chromosome breaks in two points and the released fragment it reunited after a complete turnaround

52
Q

trisomy 21

down syndrome

A

most common of the chromosomal disorders
associated with advanced maternal age
due to meiotic non-disjunction of chromosome 21 during formation of the ovum
mental retardation, epicanthic folds, flat facial profile, cardiac malformations, increased susceptibility to infection (including severe periodontal disease in childhood), large tongue, increased prevalence of acute leukemia

53
Q

incidence of down syndrome

A

45 years 1:25

54
Q

klinefelter syndrome

A

male hypogonadism that develops when there are at least two x chromosomes and one or more y chromosomes
phenotypically male
increased length of lower limbs, reduced body hair, gynecomastia, most common reason for hypogonadism
dentally- increased frequency of taurodontism

55
Q

turner syndrome

A

due to partial or complete absence of one of the x chromosomes
markedly short stature, webbing of the neck, low posterior hairline, shield like chest, high arched palate, variety of congenital cardiovascular malformations, failure to develop secondary sex characteristics, primary amenorrhea

56
Q

fluorescence in situ hybridization (FISH)

A

uses fluorescent dye-labeled probes that recognize sequences specific to chromosomal regions

57
Q

comparative genomic hybridization

A

uses different colored dyes attached to large segments of the test DNA and normal DNA, followed by hybridization
relative amts of each DNA sample are assessed based on the color of hybridized product, and gene amplification or deletion can be identified

58
Q

PCR analysis

A

amplify the DNA in question then compare the order of nucleotides of this DNA to a normal DNA
use restriction enzymes and run the segments on gel electrophoresis, compare to normal DNA
add fluorescently labeled nucleotides that are complementary to either the wild type or mutant seqeunce, then continue the PCR- determining which nucleotide is incorporated during primer extension

59
Q

indication of dna analysis prenatal

A

mother’s age >34 yrs
parent who is a carrier of a chromosomal translocation
history of previous child with chromosomal abnormality
patient who is a carrier of an x-linked disorder

60
Q

indication of dna analysis

postnatal

A 
multiple congenital anomalies
unexplained mental retardation and or developmental delay
suspected aneuploidy
suspected sex chromosomal abnormality
infertility
multiple spontaneous abortions

Path Exam 2 (7 decks)

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