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Block 1 > W1: Genetic Disease > Flashcards

W1: Genetic Disease Flashcards

1
Q

Karyotype requires arresting cell cycle at ____ stage by using ___.

A

Metaphase, colchicine

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2
Q

Define acrocentric.

A

Chromosome with centromere at one end, appearing to have only the q arm.
13,14,15,21,22

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3
Q

Turner Syndrome is an example of monosomy/trisomy, affecting the __ chromosome.

A

Monosomy, X (only one copy)

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4
Q

Translocation Down Syndrome is __% of all DS cases.

A

4%

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5
Q

How does karyotype for Robertsonian DS look like? How many total chromosomes? 14? 21? Is it balanced?

A

Total: 46
14, 14+21 (attached), 21, 21
No, unbalanced

Trisomy DS, 46, X_

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6
Q

How does karyotype for Robertsonian carrier look like? How many chromosomes? 14? 21? Is it balanced?

A

Total: 45
14, 21, 14+21
Yes, balanced

45, X_ (but normal because balanced)

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7
Q

How does karyotype for nondisjunction DS look like? How many chromosomes? 14? 21? Is it balanced?

A

Total: 47
14,14,21,21,21
No, unbalanced

Trisomy DS, 47, X_

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8
Q

What is the chance of a Robertsonian (RT) carrier passing down an unbalanced chromosome set that will cause RT DS?

A

1/3 (1/3 normal, 1/3 balanced; others lethal)

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9
Q

How does FISH work and what does it detect?

A

FISH (fluorescence in situ hybridization)

Hybridize with section of chromosome to detect a specific position or a gene on intact chromosome; detects chromosomal numeric problems or rearrangements

resolution limited to size of probe

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10
Q

What tests can be used to detect chromosomal anomalies?

A

Karyotype, FISH, chromosome painting

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11
Q

What tests can locate Robertsonian carrier?

Hint: how many chromosomes will be detected?

A

Karyotype, chromosome painting
(not FISH because it’s balanced)

(detect 45 chromosomes)

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12
Q

What tests can locate Robertsonian Down Syndrome?

Hint: how many chromosomes will be detected?

A

FISH, chromosome painting
(not karyotype because 46 chromosomes)

(46 chromosomes)

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13
Q

What tests can locate nondisjunction DS (Trisomy 21)?

Hint: how many chromosomes will be detected?

A

Karyotype, chromosome painting, FISH

47 chromosomes

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14
Q

Three types of Down Syndrome

A

Nondisjunction
Robertsonian Translocation
Mosaicism

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15
Q

Robertsonian translocation for DS usually happens between chromosomes __ and __.

A

14,21

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16
Q

Philadelphia Chromosome is caused by translocation between chromosomes __ and __; which can lead to ___.

A

9, 22;

CML (chronic myelogenous leukemia)

(Philadelphia Chromosome is balanced translocation but rearrangement activates pathway to CML)

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17
Q

What tests can be used to detect Philadelphia Chromosome?

A

FISH, karyotype, chromosome painting

visualize spacial location of translocation

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18
Q

Triploidy with extra paternal set leads to ___.

Triploidy with extra maternal set leads to ___.

A

Partial hydatidiform mole

early spontaneous abortion (SAB)

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19
Q

Name 3 tests that can detect structural rearrangement of chromosomes

A

Detected by karyotype, FISH, chromosomal painting

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20
Q

Name 3 presentations of Down Syndrome

A
  • Hypotonia (low muscle tone)
  • Dysmorphic facial features (flat nasal bridge, low-set ears,)
  • Short stature
  • Brachycephaly (“short”) with flat occiput (back of skull)
  • Short neck, loose skin on nape
  • Hands: short, broad, single transverse palmar crease
  • Curved 5th digit
  • Intellectual disability
  • Congenital heart disease (1/3; least likely to survive)
  • Increased risk for leukemia
  • Premature dementia and onset of Alzheimer’s
21
Q

Heteroploidy includes euploidy and aneuploidy. Define them.

A

Euploidy - Xn multiples of haploid (ex. triploidy)

Aneuploidy - X+n (ex. trisomy)

22
Q

The most common inborn genetic disease in North America is ___.

A

PKU (inability to metabolize aa phenylalanine)

23
Q

Unusual features of autosomal dominant inheritance?

example of disease

A
  1. reduced penetrance (people with genotype sometimes don’t express)
  2. variable expressivity (severity and onset can vary)
  3. high frequency of new mutation
24
Q

In Duchenne Muscular Dystrophy, usually male patients will present with ___ ___, very low muscle strength so need support of his arm to sit up.

A

Gower sign

25
Q

In women, __ __ __ can show up due to skewed x-inactivation, if the normal X-chromosome is inactivated early in embryonic life.

A

Duchenne Muscular Dystrophy

26
Q

Duchenne Muscular Dystrophy usually affect males/females because it’s a __ __ disorder.

A

Males; x-linked recessive

27
Q

Polymorphic markers in non-coding DNA are the basis of ___.

A

Fingerprinting

These tests tell people apart, tell relationships

RFLP – tedious; southern blot
VNTR
STR
SNP – DNA sequencing

28
Q

Sickle cell disease, PKU, CF are examples of ___ ___ disease.

A

Autosomal recessive

29
Q

Variable penetrance and expressivity are associated with autosomal dominant/recessive traits.

A

Dominant

30
Q

Duchenne muscular dystrophy, color blindness, hemophilia A are examples of ___ ___ traits.

A

X-linked recessive

31
Q

In X-linked recessive traits, mothers/fathers usually pass the traits to their sons/daughters.

A

Mothers, sons

32
Q

hypophosphatemic rickets, incontinentia pigmenti are x-linked dominant traits, where only males /both males and females are affected.

A

Both ales and females

33
Q

How do you differentiate between x-linked dominant and autosomal dominant?

A

In x-linked dominant, males never transmit trait to male, but always transmit to daughter.

34
Q

Leber’s hereditary optic atrophy, several myopathies are examples of ____ inheritance, where only mothers pass on the trait to offspring.

A

Mitochondrial (mi mutation affects skeletal muscle, brain, retina)

35
Q

What is an alternative for couple that wants to test for mutation in the fertilized egg without amniocentesis?

A

Preimplantation Genetic Diagnosis

36
Q

Fragile X is an X-linked dominant/recessive trait caused by mutation in the ___ gene.

A

Dominant, FMR1

37
Q

Penetrance with Fragile X Syndrome: What is the full mutation range for number of repeats?

A

Full mutation range: 200- >1000 repeats

38
Q

For trinucleotide repeat disorders where the length of repeat has to be measured, what are appropriate lab techniques to be used?

Examples of diseases.

A

Southern blot, PCR;

Fragile X, HD

39
Q

What technique is used to visualize the number of repeats in HD (diagnostic range?)?

A

Gel electrophoresis (40 repeats)

40
Q

List some direct mutation detection techniques

A 
Southern blot (ID DNA specific sequence)
Dot blot hybridization (ID DNA strand)
PCR (amplify specific gene)
DNA sequencing
FISH
41
Q

What method is used to detect disease whose genes have not yet been identified?

A

Linkage analysis

42
Q

___ ___ ___ is a genetic disorder is the most common cause of mental retardation.

A

Fragile X Syndrome

43
Q

Both Fragile X Syndrome and Huntington’s Disease are both ___ ___ disorder.

A

Trinucleotide repeat

44
Q

What tests are used to test for genetic diseases like Fragile X and HD?

A

Southern blot, PCR (trinucleotide repeat diseases)

45
Q

What does it mean when there is varied penetrance for HD?

What is the ultimate number?

A

The presence of symptoms are determined by number of trinucleotide repeats.

Above 40 repeats confirm diagnosis

46
Q

Define polymorphism.

A

existence of 2 or more alleles where the rare allele appears with frequency > 1% in the population

47
Q

Define SNP.

A

Single Nucleotide Polymorphism

source of variance in genome (single base mutation in DNA)

48
Q

SNP usually occurs in coding/noncoding region of the genome.

A

noncoding

49
Q

Distinguish between mosaicism and chimerism.

A

mosaicism: mutation
chimerism: fusion of fertilized zygotes during embryonic development

both contain more than one type of genes

Block 1 (26 decks)

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