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Gen Path Exam 2 > Genetic Disease > Flashcards

Genetic Disease Flashcards

1
Q

Mutations that affect germ cells can be transmitted to progeny?

A

-true

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2
Q

What are somatic mutations/

A

-these mutations can result in tumors or developmental malformations

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3
Q

What is a trinucleotide repeat mutation?

A

-amplification of sequence of 3 nucleotides

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4
Q

What is a single nucleotide polymorphism?

A
  • variation in just one nucleotide at a single site on DNA molecule
  • may be markers for multigenic complex diseases such as diabetes or hypertension
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5
Q

What are copy number variations?

A
  • different numbers of large contiguous stretches of DNA, many base pairs.
  • 1/2 involve gene-coding sequences (may account for phenotypic variation)
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6
Q

What are epigenetic changes?

A
  • modulation of gene expression without altered DNA sequence

- important in development as well as normal homeostasis

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7
Q

What is the effect of methylation on protein synthesis?

A
  • methylation of promoter regions makes them inaccessible to RNA polymerase
  • reduces protein synthesis
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8
Q

What are miRNA’s?

A

-miRNA’s inhibit translation of their target messenger RNAs into their corresponding enzymes

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9
Q

What is reduced or incomplete penetrance?

A

-person with mutant gene but doesn’t or only partially expresses it phenotypically

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10
Q

What is variable expressivity?

A

-trait seen phenotypically in all individuals having mutant gene but expressed differently among individuals

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11
Q

What is a de novo mutation?

A

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

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12
Q

What is neurofibromatosis an example of?

A
  • variable expressivity
  • AD disease with nearly 100% penetrance
  • nearly everyone with this mutation will show evidence of this relative common condition
  • highly variable expressivity
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13
Q

For autosomal recessive disorders, if the mutant gene is rare, there is a strong probability that the affected child is the product of what kind of relationship?

A

-consanguinous

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14
Q

What are the main characteristics of autosomal recessive disorders?

A
  • many present with enzyme defect that produce inborn errors of metabolism
  • carriers may possess reduced amounts of normal enzyme
  • age of onset is early in life
  • expression tends to be uniform and complete penetrance is common
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15
Q

To date, all sex-linked disorders are carried on which chromosome?

A

-X chromosome

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16
Q

What are the characteristics of X-linked disorders?

A
  • almost all recessive
  • women need 2 copies to be affected
  • all men who inherit mutation are affected
  • heterozygous females are carriers
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17
Q

What are the characteristics of lyonization?

A
  • 16 days after conception, 1 X chromosome is randomly inactivated in all cells within zygote
  • inactivated X remain inactivated in progeny
  • typically females are an even mixture of normal and abnormal chromosomes
18
Q

What is unfavorable lyonization?

A

-inactivation of an abnormally high percentage of normal X chromosomes, leading to clinical evidence of a recessive disease in a heterozygous female

19
Q

What is the one x-linked dominant that was mentioned?

A

-Oral-facial digital syndrome type I

20
Q

What are the characteristics of Marfan syndrome?

A
  • AD disorder of CT due to mutation of FBN1 gene
  • results in abnormal fibrilin 1:5000
  • tall, thin body with abnormally long legs, arms and finbers
  • dislocation of lens of eye, aortic aneurysm/Abe Lincoln, sudden death of bball players
21
Q

What are the characteristics of Ehlers-Danlos Syndromes?

A
  • 6 different types exist
  • problem of collagen synthesis
  • hypertensible skin and hypermobile joints
  • skin fragility and delayed wound healing
  • rupture of colon, large arteries
  • hernias
22
Q

What are the characteristics of familial hypercholesterolemia?

A
  • 1:500 in pop
  • mutation in gene for LDL receptor
  • results in impaired metabolism and increased LDL cholesterol in plasma
  • xanthomas and premature atherosclerosis
  • homozygotes die of MI before age 20
  • treat with clot buster- Iomitapide (very strong med)
23
Q

What are the characteristics of phenylketonuria?

A
  • AR disorder 1:10000 caucasian infants
  • lack of phenylalanine hydroxylase–> hyperphenylalaninemia and PKU
  • Affected infants normal at birth–> elevated phenylalanine levels impair brain development and mental retardation evident by 6 mo of age
  • screening of newborns mandatory in U.S.
  • restriction of dietary phenylalanine will prevent metal retardation
24
Q

What are the characteristics of lysosomal storage diseases?

A
  • AR transmission
  • commonly affect infants and young children
  • accumulation of large molecules in macrophages with hepatosplenomegaly
  • frequent CNS involvement, mental retardation/early death
25
Q

What are the main lysosomal storage diseases?

A
  • Tay-Sachs
  • Niemann-Pick
  • Gaucher
26
Q

What is mucopolysaccharidoses?

A
  • coarse facial features
  • clouding of cornea
  • joint stiffness
  • mental retardation
  • 7 variants described
27
Q

What are the characteristics of hurler disease?

A
  • AR, caused by deficiency of laronidase
  • life expectancy 6-10 yrs if left untreated
  • cost of enzyme yearly–> $300k/year
28
Q

What are the characteristics of Hunter syndrome?

A
  • X linked
  • L-iduronate sulfatase
  • absence of corneal clouding and milder clinical course
  • similar to Hurler disease
29
Q

Chromosomal abnormalities are thought to contribute to what percentage of 1st trimester spontaneous abortions?

A

-50%

30
Q

What is polyploidy?

A

-increased multiple of chromosome number

31
Q

What is aneuploidy?

A
  • extra chromosome or missing one chromosome

- any number that is not direct multiple of normal chromosome count

32
Q

Structural abnormalities also occur due to chromosome breakage following what cellular processes?

A

-loss or rearrangement of genetic material

33
Q

What are the characteristics of trisomy 21?

A
  • most common of chromosome disorders
  • associated with advanced maternal age
  • > 45 1:25
  • due to meiotic non-disjunction of chromosome 21 during formation of ovum
  • mental retardation; flat facial profile; cardiac malformations; increased susceptibility to infection; large tongue; increased prevalence of acute leukemia
34
Q

What are the characteristics of Klinefelter syndrome?

A
  • male hypogonadism XXY
  • increased length of lower limbs, reduced body hair; gynecomastia; most common reason for hypogonadism
  • dentally- increased frequency of taurodontism
35
Q

What are the characteristics of turner syndrome?

A
  • Due to partial or complete absence of one X chromosome
  • short stature, webbing of neck, low posterior hairline, shield-like chest, high-arched palate, variety of congenital CV malformations
  • failure to develop secondary sex characteristics; primary amenorrhea
36
Q

What is fluorescence in situ hybridization?

A

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

37
Q

What is chromosomal genomic hybridization?

A
  • amounts of DNA labeled with different color labels

- assess amounts to determine gene amplification or deletion

38
Q

Steps of molecular diagnosis of genetic disorders

A
  • PCR
  • Compare order of nucleotides to normal DNA
  • use restriction enzymes to cut segments and run on gel, compare to normal
  • add fluorescent labels to nucleotides to check where nucleotide is incorporated during primer extension
39
Q

What are the prenatal indicators for genetic analysis?

A
  • mother’s age > 34
  • Parent with chromosomal translocation
  • Hx of previous child with chromosomal abnormality
  • Parent who is a carrier of x-linked disorder
40
Q

What are the postnatal indicators for genetic analysis?

A
  • multiple congenital anomalies
  • unexplained metal retardation/developmental delay
  • suspected down syndrome
  • suspected sex chromosome abnormality
  • infertility
  • multiple spontaneous abortions

Gen Path Exam 2 (12 decks)

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