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DMD 5246 > Bikman - Genetic Disorders > Flashcards

Bikman - Genetic Disorders Flashcards

1
Q

Chromosomal mutations

A

Any inherited alteration of genetic material.

  1. Base pair substitution
  2. Frameshift mutation
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2
Q

What is base pair substitution and what are possible outcomes?

A

One base pair is substituted for another

Possible outcomes:

  1. Silent
  2. Missense
  3. Nonsense
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3
Q

What is a frameshift mutation?

A

Insertion or deletion of one or more base pairs.

Causes a change in the entire “reading frame”

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4
Q

What are non-mutation alterations in chromosomes?

A
  1. Polymorphisms
  2. Epigenetic changes
  3. Alterations in non-coding RNAs
  4. Translocation
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5
Q

What is a polymorphism? (SNP and copy number variation)

A

(Non mutation alteration)

Single nucleotide polymorphisms: Common variation at a single nt position

Copy number variations: Abnormal # of copies of one or more sections of the DNA

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6
Q

What is the difference between SNP and point mutation?

A

If it occurs in <1% of people, it’s a point mutation; occurs in >1%, it’s a SNP

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7
Q

Epigenetic changes

A

(Non mutation alteration)

Non-DNA changes; i.e. alterations in gene or protein expression

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8
Q

Alterations in non-coding RNAs

A

(Non mutation alteration)

Regulatory genes that do not code for proteins

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9
Q

Translocation

A

(Non mutation alteration)

Exchanging genetic material between non-homologous chromosomes.
Occurs when two chromosomes break and the segments are rejoined in an abnormal fashion.

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10
Q

Chromosome aberrations

A 
Euploid
Polyploid
Aneuploid
Disjunction
Non disjunction
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11
Q

Euploid cells

A

(Chromosome abberation)

Have normal # of chromosomes
Different for haploid vs. diploid

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12
Q

Polyploid cells

A

(Chromosome aberration)

Cell has a multiple of 23

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13
Q

Triploidy

A

Three copies of every chromosome

3*23 = 69

Embryonic lethal; ~10% of known miscarriages

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14
Q

Tetraploidy

A

Four copies of every chromosome

4*23 = 92

Embryonic lethal; ~10% of known miscarriages

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15
Q

What is aneuploidy and what are some examples of aneuploidy?

A

(Chromosome aberration)

Somatic cell that doesn’t have a multiple of 23 chromosomes.
One too many, or one too few

Trisomy
Monosomy

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16
Q

Trisomy

A

3 copies of one chromosome

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17
Q

Monosomy

A

1 copy of any one chromosome

*Lethal, but infants can survive with trisomy of certain chromosomes

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18
Q

Disjunction

A

(Chromosome aberration)

Normal separation of chromosomes during cell division.

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19
Q

Non-disjunction

A

(Chromosome aberration)

Usually the cause of aneuploidy.

Failure of homologous chromosomes or sister chromatids to separate

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20
Q

If a human fetus has 45 chromosomes, it would be called…

A

Aneuploidy

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21
Q

What are some examples of autosomal aneuploidy?

A

Trisomy 13
Trisomy 18
Trisomy 21

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22
Q

Trisomy 13

A

(Autosomal aneuploidy)

Patau Syndrome
Polydactyly
Mental retardation
Microcephaly

Usually lethal early in life due to heart deformities

23
Q

Trisomy 18

A

(Autosomal aneuploidy)

*Edwards Syndrome*
Kidney malformations
Protruding intestines
Mental retardation
Small size

Usually lethal early in life due to heart deformities.

24
Q

Trisomy 21

A

(Autosomal aneuploidy)

Down Syndrome
Risk increases with maternal and/or paternal age.
Best known example of aneuploidy

25
Q

What are some examples of sex chromosome aneuploidy?

A

Trisomy X
Turner Syndrome
Klinefelter Syndrome

26
Q

Trisomy X

A

(Sex Chromosome Aneuploidy)

Little physical manifestation - Lyonization.

Symptoms can vary from no overt symptoms to sterility, menstrual irregularity, and/or mental retardation - can worsen with each additional X chromosome

27
Q

Turner Syndrome

A

(Sex Chromosome Aneuploidy)

XO female

Undeveloped ovaries (sterile)
Short stature
Webbing of neck
Edema
Underdeveloped breasts; wide nipples (Shield's chest)
Out-turned arms at elbows
Low hairline at back of neck
28
Q

Klinefelter Syndrome

A

(Sex Chromosome Aneuploidy)

XXY males

Male appearance
Can be fertile
Possible modest breast development at puberty
Underdeveloped male genitals
Sparse body hair
Long limbs

XXXY, XXXXY - Abnormalities increase with each X

29
Q

Which of the following is an example of trisomy?

A. Fragile X
B. Turner Syndrome
C. Klinefelter Syndrome
D. Cris du chat Syndrome

A

C. Klinefelter

30
Q

Autosomal dominant vs. Autosomal recessive disorders

A

Dominant doesn’t skip generations doesn’t generate carrier progeny, only normal and affected.

Recessive may skip generations and may produce carrier progeny, in additional to normal or affected.

31
Q

If both parents are affected with autosomal dominant disorder, what is the recurrence in the offspring?

A

~3/4

32
Q

If one parent is normal and the other parent is affected with autosomal dominant disorder, what is the recurrence in offspring?

A

~1/2

33
Q

What are some examples of autosomal dominant disorders?

A

Marfan syndrome
Ehlers-Danlos Syndrome
Treacher Collins Syndrome

34
Q

What is Marfan Syndrome and what are the features of it?

A

(Autosomal Dominant Disorder)

A disorder of CT, manifested principally by changes in the skeleton, eyes, and CV system.

Features:

  • Unusually tall with long extremities
  • Ectopica lentis: bilateral subluxation of eye lens
  • CV lesions: Mitral valve prolapse
35
Q

What is Ehlers-Danlos Syndrome and what are the features of it?

A

(Autosomal Dominant Disorder)

A group of diseases characterized by defects in collagen synthesis or structure.

Features:

  • Skin and joint hypermobility
  • Easy bruising

Gorlin’s Sign is can be an indicator

36
Q

What is Treacher Collins Syndrome and what are features of it?

A

(Autosomal Dominant Disorder)

Results from the abnormal development from the first and second branchial arches.

Features:

  • Underdeveloped mandible
  • Downward slating palpebral fissures
  • Possible cleft palate
37
Q

What is penetrance?

A

The percentage of individuals with a specific genotype who also express the expected phenotype.

38
Q

What is incomplete penetrance? What is an example of incomplete penetrance?

A

Someone who has the gene for a disease but doesn’t express the disease,

i.e. Retinoblastoma

39
Q

What is expressivity? What is an example?

A

The variation in a phenotype associated with a particular genotype.

i.e. von Recklinghausen disease (neurofibromatosis)

40
Q

What is von Recklinghausen disease?

A

Example of expressivity.

Autosomal dominant.
Disease can vary from dark spots on skin to malignant neurofibromas, scoliosis, gliomas, neuromas, etc.

41
Q

What can increase the risk of expressing autosomal recessive disorders?

A

Consanguinity

42
Q

What are the two types of autosomal recessive storage diseases?

A

Lysosomal

Glycogen

43
Q

What autosomal recessive diseases are classified as lysosomal storage diseases?

A
  1. Gaucher’s disease
  2. Tay-Sachs disease
  3. Niemann-Pick disease
44
Q

What are the deficient enzymes, accumulating metabolites, and affected cells of Gaucher’s Disease? What are histologic signs of it?

A

Deficient enzyme:
Glucocerebrosidase

Accumulating metabolite: Glucocerebroside

Affected cells: Macrophage

Histologic sign: Enlarged macrophages in the spleen

45
Q

What are the deficient enzymes, accumulating metabolites, and affected cells of Tay-Sachs disease? What are histologic signs of it?

What population is Tay-Sachs most prevalent in?

A

Deficient enzyme: Hexosaminidase A

Accumulating metabolite: G Ganglioside

Affected cells: Neurons

Histologic sign: Enlarged pale neurons.

Leads to motor and mental deficits, blindness, dementia.

Particularly prevalent among Ashkenazi Jews.

46
Q

What are the deficient enzymes, accumulating metabolites, and affected cells of Niemann-Pick disease? What are histologic signs of it?

A

Deficient enzyme: Sphingomyelinase

Accumulating metabolite: Sphingomyelin

Affected cells: Neurons and phagocytes

Histologic sign: Kuppfer cells have foamy appearance

47
Q

What diseases are classified as autosomal recessive glycogen storage diseases?

A
  1. Type I: von Gierke’s
  2. Type II: Pompe’s
  3. Type III: Cori’s
  4. Type IV: Brancher Glycogenosis/Anderson’s
  5. Type V: McArdle’s Syndrome
48
Q

What are the deficient enzymes, affected tissues, and histiologic signs of von Gierke’s disease (Type I)?

A

Deficient Enzyme: Glucose-6-phosphatase

Affected tissue: Liver and kidney

Histiologic sign: Foamy hepatocyte

49
Q

What are the deficient enzymes, affected tissues, and histiologic signs of Pompe’s disease (Type II)?

A

Deficient Enzyme: Lysosomal glucosidase

Affected tissue: Heart

Histiologic sign: Large vacuoles in cardiomyocytes

50
Q

What are the deficient enzymes, affected tissues, and histiologic signs of Cori’s disease (Type III)?

A

Deficient Enzyme: Debranching enzyme

Affected tissue: Heart, liver, skeletal muscle

Histiologic sign: Enlarged hepatocytes

51
Q

What are the deficient enzymes, affected tissues, and histiologic signs of Brancher Glycogenosis/Anderon’s (Type IV)?

A

Deficient Enzyme: Branching enzyme

Affected tissue: Heart liver, skeletal muscle, brain

Histiologic sign: Enlarged hepatocytes

52
Q

What are the deficient enzymes, affected tissues, and histiologic signs of McArdle’s Syndrome (Type V)?

A

Deficient Enzyme: Muscle phosphorylase

Affected tissue: Skeletal muscle

Histiologic sign: Large vacuoles in myocytes

53
Q

What is Chediak-Higashi Syndome and what are some features of it? What are histiologic signs?

A

(Autosomal Recessive Disorder)

Arises from a mutation of a lysosomal trafficking regulator gene (LYST).

  • Partial albinism
  • Photophobia
  • Compromised immunity
  • Neuropathy

Histiologic sign: Fusion of lysosomal granules

54
Q

What are some examples of sex-linked disorders?

A

Hemophilia A and B
Duchenne Muscular Dystrophy
Red-green color blindness

DMD 5246 (3 decks)

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