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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
Explain what an autosomal recessive disorder is.
a trait is expressed if the individual has both genes at a given locus mutated/affected (homozygous)
26
What is the largest group of mendelian disorders?
autosomal recessive disorders
27
True or False: If a mutation is rare in an autosomal recessive disorder, the affected person is likely from a consanguineous (same ancestor) relationship.
True
28
What are some characteristics of autosomal recessive disorders?
* 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
29
What is another name for sex-linked disorder?
x-linked disorder
30
Are there any Y-linked diseases?
No, hairy ears MAY be carried on y-chromosome.
31
Are all sex-linked diseases X-linked?
Yes
32
Who is typically affected by an x-linked mutations/disease?
homozygous females males (because they only have 1 x chromosome) Females where lyonization has occurred
33
True or False: | Almost all X-linked disorders are recessive.
True
34
Who are carriers in X-linked disorders?
heterozygous females
35
What is lyonization?
inactivation of 75% or more of one X chromosome in all cells of a zygote. * continues in progeny of the cell
36
Does lyonization effect the maternal or paternal X chromosome?
It can effect either
37
Define unfavorable lyonization.
inactivation of an abnormally high percentage of X chromosomes.
38
Who is affected in an X-linked dominant disease?
Heterozygous females homozygous females hemizygous males (oral-facial-digital syndrome type 1)
39
What diseases are caused by structural protein mutations?
Marfan Syndrome | Ehlers-Danlos Syndromes
40
What is Marfan Syndrome?
``` Autosomal dominant disorder of connective tissue abnormal fibrillin (necessary for normal elastic fiber production) ```
41
What gene is affected in Marfan Syndrome?
FBN1 gene is mutated
42
What are symptoms/characteristics of Marfan syndrome?
Tall, thin body long extremities dislocation of the lens in the eye aortic aneurysm -->heart failure or aortic rupture
43
What is/are Ehlers-Danlos Syndrome(s)?
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
What are some characteristics/symptoms of Ehlers-Danlos?
hyperextensible skin/joints fragile skin - delayed wound healing rupture of colon/large arteries hernias
45
What disease(s) is/are caused by mutations in the receptor proteins?
Familial Hypercholesterolemia
46
What is familial hypercholesterolemia?
mutation in the gene for the LDL receptor | * results in increased LDL in plasma (duh)
47
How prevalent is familial hypercholesterolemia?
1:500 - very common inherited disease
48
What are symptoms of familial hypercholesterolemia?
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
What drug treats homozygous individuals with familial hypercholesterolemia?
lomitapide
50
What diseases are caused by mutations in genes encoding enzyme proteins?
Phenylketonuria Lysosomal Storage Diseases Hurler Disease (MPS type I) Hunter Syndrome
51
What is Phenylketonuria?
autosomal recessive disorder | lack of phenylalanine hydroxylase - too much phenylalanine (building block of proteins) in blood
52
What symptoms are caused by phenylketonuria?
impair brain development mental retardation by age of 6 months * mandatory to screen in newborns in the US
53
Who is typically affected by Phenylketonuria?
Caucasian infants
54
What is lysosomal storage disease?
autosomal recessive | accumulation of insoluble large molecules in macrophages w/hepatosplenomegaly
55
Who is affected by lysosomal storage disease?
infants and young children
56
What are symptoms of Lysosomal storage disease?
CNS issues mental retardation early death
57
Name different examples of a lysosomal storage disease.
``` Tay-Sachs disease Niemann-Pick disease Gaucher disease mucopolysaccharidoses *Hurler Disease (MPS type I) *Hunter Syndrome ```
58
What are symptoms seen in a person with mucopolysaccharidoses?
``` course facial hair clouding of the cornea joint stiffness mental retardation 7 different types? ```
59
What is Hurler Disease?
It is a mucopolysaccharidosis type IH. Autosomal recessive Deficiency in alpha-L-iduronidase
60
What is the life expectancy of someone with Hurler Disease?
6-10 yrs if untreated; | tx with bone marrow transplant or enzyme replacement ($300,000/year)
61
What is Hunter Syndrome?
X-linked | deficiency in L-iduronate sulfatase
62
What differences between Hunter syndrome and Hurler disease clinically?
Hunter syndrome - no corneal clouding, more mild clinically
63
What are multifactorial (polygentic) disorders
two or more genes are responsible, plus environmental influences
64
Examples of multifactorial disorders?
diabetes, hypertension, gout, schizophrenia, bipolar?? governs many physiologic traits (height, weight, bp, hair color)
65
What is a karyotype?
number and visual appearance of chromosomes in the nuclei of a cell
66
What is normal chromosome count in a human?
46 chromosomes | 23 pairs ^^
67
What is the prevalence of chromosomal abnormalities?
1:200 | this is the result of 50% of 1st trimester spontaneous abortions
68
Define euploid.
a normal chromosome count | 2 X 23 = 46
69
Define polyploidy.
increase in chromosomes that is a multiple of the normal chromosome count: 3 X 23 4 X 23
70
Define aneuploidy.
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
How many chromosomes are in someone with trisomy?
47; person is aneuploidy
72
How many chromosomes in someone with monosomy?
45; person is aneuploidy
73
How do structural abnormalities occur?
chromosome breakage by loss or rearrangement of material
74
Define translocation.
transfer of part of a chromosome to another nonhomologous chromosome.
75
Define reciprocal translocation.
normal exchange of chromosome fragments between two chromosomes.
76
Define deletion.
loss of a portion of chromosome
77
Define inversion.
a chromosome breaks at two points - released fragment is reunited after complete turnaround
78
Name a cytogenetic disorder involving autosomes.
Trisomy 21 (Down Syndrome)
79
What is trisomy 21/Down Syndrome?
meiotic non-disjunction of chromosome 21 during formation of the ovum * associated with advanced maternal age
80
Symptoms of Trisomy 21
mental retardation epicanthic folds (folding of skin inner corner of eye) cardiac malformations increased susceptibility to infection (periodontal disease) large tongue acute leukemia
81
What are some cytogenetic disorders involving sex chromosomes?
Klinefelter Syndrome | Turner Syndrome
82
What is Klinefelter Syndrome?
male hypogonadism | male has 2 x chromosomes and 1 or more y chromosomes (XXY)
83
Symptoms of Klinefelter syndrome.
long lower limbs reduced body hair gynecomastia (swelling of breast tissue) taurodontism (pulp chamber is enlarged)
84
What is Turner Syndrome?
partial or complete absence of one X chromosomes
85
Symptoms of Turner syndrome?
``` short stature webbing neck low posterior hairline high-arched palate congenital cardio malformations failure of developed secondary sex characteristics amenorrhea (no period) ```
86
How can you diagnose genetic disease?
fluorescence in situ hybridization (FISH) Comparative genomic hybridization Molecular diagnosis of genetic disorders Next generation sequencing
87
What is Fluorescence in situ hybridization (FISH)
use fluorescent dye that recognize sequences specific to chromosomal regions
88
What is Comparative genomic hybridization
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
What is molecular diagnosis of genetic order sequence?
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
What is next generation sequencing?
parallel sequencing, | more sensitive detection of allelic variants
91
Prenatal indications for genetic analysis.
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
Postnatal indications of genetic analysis
``` multiple congenital abnormalities unexplained mental retardation developmental delay suspected aneuploidy suspected sex chromosomal abnormality infertility multiple spontaneous abortions ```

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