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Gen Path > Exam 2 - Genetics > Flashcards

Exam 2 - Genetics Flashcards

1
Q

How many pairs of autosomal chromosomes?

A

22 pairs

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2
Q

How many pairs of sex chromosomes?

A

1 pair

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3
Q

What does a gene contain?

A

genetic information required to produce protein

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4
Q

Why are proteins important?

A

needed to perform necessary body function

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5
Q

What does it mean if a person is heterozygous for a disorder?

A

One chromosome in the pair is affected/mutated

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6
Q

Term used if both chromosome pairs of a gene locus are mutated

A

homozygous

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7
Q

Term used for a permanent change in DNA

A

Mutation

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8
Q

Can a mutation affecting the germ cells be hereditary?

A

Yes, it can be passed on to the next generation/progeny

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9
Q

What occurs if somatic cells are mutated?

A

Can result in a tumor or developmental malformation

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10
Q

What are the different types of mutations?

A

point mutations
frameshift mutations
trinucleotide repeat mutations

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11
Q

Describe a point mutation

A

a single nucleotide base is substituted

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12
Q

Describe a frameshift mutation

A

insertion or deletion of one or two base pairs. This alters the reading frame of the DNA Strand

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13
Q

Describe Trinucleotide repeat mutations.

A

amplification/repetition of a 3 nucleotide sequence

Fragile X syndrome

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14
Q

What are other alterations in protein coding that are not mutations?

A

polymorphisms
copy number variations
epigenetic changes
alterations in non-coding RNAs (miRNAs)

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15
Q

What is a polymorphism?

A

variation in one nucleotide at a single site on the DNA molecule
* may be markers for multigenetic complex diseases (diabetes, hypertension)

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16
Q

What are copy number variations?

A

number of copies of a gene varies from one individual to another.
* ranges from 1,000 to a million base pairs

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17
Q

What alteration in protein coding may account for phenotypic variation?

A

copy number variations

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18
Q

What are epigenetic changes?

A

modulation of gene expression without altering DNA sequence.

  • may change phenotype, but not genotype.
  • may be achieved by adding a methyl group to promoter regions to inhibit RNA polymerase from binding. –> proteins can not be made.
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19
Q

What do alterations in non-coding RNAs (micro-RNAs) cause?

A

inhibits translation of their target messenger RNAs (mRNA) into corresponding proteins

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20
Q

Define autosomal dominant disorders/disease and when it will be present.

A

A dominant allele of an autosome has an altered gene locus. It will be present even if the person has only one mutated gene locus.

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21
Q

What are some characteristics of autosomal dominant disorders?

A

most people have an outward physical change

There may be a delayed age of onset. (Huntington disease)

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22
Q

Define reduced/incomplete penetrance.

A

A person has a mutant gene, but doesn’t express it at all or only partially expresses the phenotype.

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23
Q

Define variable expressivity.

A

The trait/mutation is expressed in all individuals with the mutant gene, but is expressed differently in individuals.

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24
Q

Define de novo mutation.

A

an individual’s parents may not be affected because the disease is a new mutation.

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25
Q

Explain what an autosomal recessive disorder is.

A

a trait is expressed if the individual has both genes at a given locus mutated/affected (homozygous)

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26
Q

What is the largest group of mendelian disorders?

A

autosomal recessive disorders

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27
Q

True or False:
If a mutation is rare in an autosomal recessive disorder, the affected person is likely from a consanguineous (same ancestor) relationship.

A

True

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28
Q

What are some characteristics of autosomal recessive disorders?

A
  • Enzyme defects -> inborn errors of metabolism (even in heterozygous individuals - decrease in normal enzyme)
  • early age of onset
  • complete penetrance is common
  • defect may be more uniform across individuals
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29
Q

What is another name for sex-linked disorder?

A

x-linked disorder

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30
Q

Are there any Y-linked diseases?

A

No, hairy ears MAY be carried on y-chromosome.

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31
Q

Are all sex-linked diseases X-linked?

A

Yes

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32
Q

Who is typically affected by an x-linked mutations/disease?

A

homozygous females
males (because they only have 1 x chromosome)
Females where lyonization has occurred

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33
Q

True or False:

Almost all X-linked disorders are recessive.

A

True

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34
Q

Who are carriers in X-linked disorders?

A

heterozygous females

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35
Q

What is lyonization?

A

inactivation of 75% or more of one X chromosome in all cells of a zygote.
* continues in progeny of the cell

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36
Q

Does lyonization effect the maternal or paternal X chromosome?

A

It can effect either

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37
Q

Define unfavorable lyonization.

A

inactivation of an abnormally high percentage of X chromosomes.

38
Q

Who is affected in an X-linked dominant disease?

A

Heterozygous females
homozygous females
hemizygous males
(oral-facial-digital syndrome type 1)

39
Q

What diseases are caused by structural protein mutations?

A

Marfan Syndrome

Ehlers-Danlos Syndromes

40
Q

What is Marfan Syndrome?

A 
Autosomal dominant disorder of connective tissue
abnormal fibrillin (necessary for normal elastic fiber production)
41
Q

What gene is affected in Marfan Syndrome?

A

FBN1 gene is mutated

42
Q

What are symptoms/characteristics of Marfan syndrome?

A

Tall, thin body
long extremities
dislocation of the lens in the eye
aortic aneurysm –>heart failure or aortic rupture

43
Q

What is/are Ehlers-Danlos Syndrome(s)?

A

Problem with collagen synthesis
* there is more than one type of (30) collage in the body so there is more than one type of Ehlers-Danlos syndrome (6 types)

44
Q

What are some characteristics/symptoms of Ehlers-Danlos?

A

hyperextensible skin/joints
fragile skin - delayed wound healing
rupture of colon/large arteries
hernias

45
Q

What disease(s) is/are caused by mutations in the receptor proteins?

A

Familial Hypercholesterolemia

46
Q

What is familial hypercholesterolemia?

A

mutation in the gene for the LDL receptor

* results in increased LDL in plasma (duh)

47
Q

How prevalent is familial hypercholesterolemia?

A

1:500 - very common inherited disease

48
Q

What are symptoms of familial hypercholesterolemia?

A

xanthomas
premature atherosclerosis (plaque build up)
homozygous individuals have 5x more LDL than normal levels (often die before 20 of an MI)
Heterozygous individuals have 2-3X more LDL than normal person.

49
Q

What drug treats homozygous individuals with familial hypercholesterolemia?

A

lomitapide

50
Q

What diseases are caused by mutations in genes encoding enzyme proteins?

A

Phenylketonuria
Lysosomal Storage Diseases
Hurler Disease (MPS type I)
Hunter Syndrome

51
Q

What is Phenylketonuria?

A

autosomal recessive disorder

lack of phenylalanine hydroxylase - too much phenylalanine (building block of proteins) in blood

52
Q

What symptoms are caused by phenylketonuria?

A

impair brain development
mental retardation by age of 6 months
* mandatory to screen in newborns in the US

53
Q

Who is typically affected by Phenylketonuria?

A

Caucasian infants

54
Q

What is lysosomal storage disease?

A

autosomal recessive

accumulation of insoluble large molecules in macrophages w/hepatosplenomegaly

55
Q

Who is affected by lysosomal storage disease?

A

infants and young children

56
Q

What are symptoms of Lysosomal storage disease?

A

CNS issues
mental retardation
early death

57
Q

Name different examples of a lysosomal storage disease.

A 
Tay-Sachs disease
Niemann-Pick disease
Gaucher disease
mucopolysaccharidoses
   *Hurler Disease (MPS type I)
  *Hunter Syndrome
58
Q

What are symptoms seen in a person with mucopolysaccharidoses?

A 
course facial hair
clouding of the cornea
joint stiffness
mental retardation
7 different types?
59
Q

What is Hurler Disease?

A

It is a mucopolysaccharidosis type IH.
Autosomal recessive
Deficiency in alpha-L-iduronidase

60
Q

What is the life expectancy of someone with Hurler Disease?

A

6-10 yrs if untreated;

tx with bone marrow transplant or enzyme replacement ($300,000/year)

61
Q

What is Hunter Syndrome?

A

X-linked

deficiency in L-iduronate sulfatase

62
Q

What differences between Hunter syndrome and Hurler disease clinically?

A

Hunter syndrome - no corneal clouding, more mild clinically

63
Q

What are multifactorial (polygentic) disorders

A

two or more genes are responsible, plus environmental influences

64
Q

Examples of multifactorial disorders?

A

diabetes, hypertension, gout, schizophrenia, bipolar??

governs many physiologic traits (height, weight, bp, hair color)

65
Q

What is a karyotype?

A

number and visual appearance of chromosomes in the nuclei of a cell

66
Q

What is normal chromosome count in a human?

A

46 chromosomes

23 pairs ^^

67
Q

What is the prevalence of chromosomal abnormalities?

A

1:200

this is the result of 50% of 1st trimester spontaneous abortions

68
Q

Define euploid.

A

a normal chromosome count

2 X 23 = 46

69
Q

Define polyploidy.

A

increase in chromosomes that is a multiple of the normal chromosome count:
3 X 23
4 X 23

70
Q

Define aneuploidy.

A

Any number of chromosome that is not a multiple of normal chromosome count
2 X 23 + 1 = 47 - trisomy
2 X 23 - 1 = 45 - monosomy

71
Q

How many chromosomes are in someone with trisomy?

A

47; person is aneuploidy

72
Q

How many chromosomes in someone with monosomy?

A

45; person is aneuploidy

73
Q

How do structural abnormalities occur?

A

chromosome breakage by loss or rearrangement of material

74
Q

Define translocation.

A

transfer of part of a chromosome to another nonhomologous chromosome.

75
Q

Define reciprocal translocation.

A

normal exchange of chromosome fragments between two chromosomes.

76
Q

Define deletion.

A

loss of a portion of chromosome

77
Q

Define inversion.

A

a chromosome breaks at two points - released fragment is reunited after complete turnaround

78
Q

Name a cytogenetic disorder involving autosomes.

A

Trisomy 21 (Down Syndrome)

79
Q

What is trisomy 21/Down Syndrome?

A

meiotic non-disjunction of chromosome 21 during formation of the ovum
* associated with advanced maternal age

80
Q

Symptoms of Trisomy 21

A

mental retardation
epicanthic folds (folding of skin inner corner of eye)
cardiac malformations
increased susceptibility to infection (periodontal disease)
large tongue
acute leukemia

81
Q

What are some cytogenetic disorders involving sex chromosomes?

A

Klinefelter Syndrome

Turner Syndrome

82
Q

What is Klinefelter Syndrome?

A

male hypogonadism

male has 2 x chromosomes and 1 or more y chromosomes (XXY)

83
Q

Symptoms of Klinefelter syndrome.

A

long lower limbs
reduced body hair
gynecomastia (swelling of breast tissue)
taurodontism (pulp chamber is enlarged)

84
Q

What is Turner Syndrome?

A

partial or complete absence of one X chromosomes

85
Q

Symptoms of Turner syndrome?

A 
short stature
webbing neck
low posterior hairline
high-arched palate
congenital cardio malformations
failure of developed secondary sex characteristics
amenorrhea (no period)
86
Q

How can you diagnose genetic disease?

A

fluorescence in situ hybridization (FISH)
Comparative genomic hybridization
Molecular diagnosis of genetic disorders
Next generation sequencing

87
Q

What is Fluorescence in situ hybridization (FISH)

A

use fluorescent dye that recognize sequences specific to chromosomal regions

88
Q

What is Comparative genomic hybridization

A

use different colored dyes attached to large segments test DNA & normal DNA
* color of the hybridized product is analyzed and gene amplification or deletion can be identified

89
Q

What is molecular diagnosis of genetic order sequence?

A
  1. PCR analysis - amplify the DNA in question
  2. compare the order of nucleotides to a normal DNA sequence
  3. use restriction enzymes and run segments on a gel electrophoresis (compare test and normal DNA)
  4. Add fluorescently labeled nucleotides complementary to wild type or mutant sequence. continue PCR. determine which nucleotide is incorporated during primer extension.
90
Q

What is next generation sequencing?

A

parallel sequencing,

more sensitive detection of allelic variants

91
Q

Prenatal indications for genetic analysis.

A

mom is older than 34
parent is a carrier of a chromosomal translocation
Hx of previous child with chromosomal abnormality
parent who is a carrier of X-linked disorder

92
Q

Postnatal indications of genetic analysis

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

Gen Path (7 decks)

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