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Biochem V > Chromosomal Aberrations > Flashcards

Chromosomal Aberrations Flashcards

1
Q

What is the percentage of chromosomal aberrations at birth? Pregnancies?

A
  1. 2%

0. 5%

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2
Q

What are the two main processes that generate structural chromosomal aberrations?

A

healing of DNA by double stranded breaks

unbalanced recombination

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3
Q

How does Cri-du-chat arise?

A

deletion on chromosome 5

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4
Q

What is DiGeorge syndrome also known as?

A

velocardiofacial syndrome

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5
Q

How does DiGeorge syndrome arise?

A

microdeletion on chromosome 22

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6
Q

What is the mode of inheritance for DiGeorge Syndrome?

A

autosomal dominant

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7
Q

Where does a translocation insert a chromosome? Insertion?

A

end of another chromosome

insertion = middle

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8
Q

What happens in a Robertsonian translocation?

A

long and short arms of a chromosome are exchanged

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9
Q

What is the most common chromosomal aberration in humans?

A

Robertsonian translocation

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10
Q

Which chromosomes are often involved in a Robertsonian translocation?

A

13q and 14q

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11
Q

What is an inversion?

A

chromosome suffers two breaks and is re-inserted in the wrong orientation

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12
Q

What is a balanced chromosomal rearrangment?

A

no change in the amount of genetic material

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13
Q

What can nondisjunction in meiosis lead to?

A

cells with surplus or missing chromosomes

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14
Q

What are the two processes that generate structural chromosomal aberrations?

A

non-homologous end joining and

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15
Q

What is more severe, deletions or duplications?

A

deletions

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16
Q

How does Cru du Chat arise?

A

deletion on chromosome 5

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17
Q

How does diGeorge syndrome arise?

A

microdeletion on chromosome 22

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18
Q

What is DiGeorge syndrome also known as?

A

velocardiofacial syndrome

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19
Q

What is the most common phenotype of DiGeorge syndrome?

A

congenital heart defect

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20
Q

Where does an insertion move a chromosome?

A

into the middle of another chromosome

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21
Q

What does a translocation move a chromosome?

A

attaches it to the end

22
Q

How is the Philadelphia Chromosome generated?

A

a translocation between chromosome 9 and 22

23
Q

Regarding the Philadelphia Chromosome, what specific genes are traslocated?

A

ABL tyrosine kinase from 9 to the BCR region on 22

24
Q

What is a Robertsonian translocation?

A

long and short arm of two chromosomes are exchanged

25
Q

What is the most common chromosomal rearrangement?

A

Robertsonian Translocation of 13q and 14q

26
Q

What is an inversion?

A

when a chromosome suffers two breaks and the broken-off fragment is re-inserted into the wrong direction

27
Q

What happens when an inverted chromosome pairs with its homolog during meiosis?

A

an inversion loop is created

28
Q

Regarding a Robertsonian Translocation, what usually happens to the short arm containing chromosome?

A

it gets lost

29
Q

Regarding the philadelphia chromosome, what gene moves to what chromosome?

A

ABL from 9 moves to BCR of 22

30
Q

A robertsonian translocation often involves which two chromosomes?

A

13q and 14q

31
Q

What will an inverted chromosome form in meiosis?

A

inversion loop

32
Q

Regarding an inversion loop, what can meiosis create?

A

a dicentric or acentric chromosome

33
Q

When do patients usually become aware of their balanced translocation?

A

reproduction

34
Q

What cells is most frequently used to perform karyotypes?

A

lymphocytes

35
Q

What cell cycle phase are chromosomes arrested in during karyotyping?

A

metaphase

36
Q

Where does methylation of DNA occur?

A

on cytosine residues in CpG islands

37
Q

What protein is responsible for introducing de novo methylation of DNA?

A

DNMT 3a and 3b

38
Q

What protein is defective in Rett Syndrome?

A

methyl cytosine binding protein

39
Q

What characteristic of DNA is lost during Rett Syndrome?

A

Loss of txn silencing

40
Q

How is Rett Disease transmitted?

A

X-linked dominant

41
Q

Where does the silencing of histones occur via acetylation?

A

tail

42
Q

In addition to acetylation, what are three other modifications of histones?

A

phosphorylation, ubiquitination and methylation

43
Q

What protein binds methylated histones?

A

HP1

44
Q

What happens to histones after they are deacetylated?

A

they become methylated

45
Q

What do HP1 proteins bind?

A

histone methylase

46
Q

What are MBPs?

A

methylcytosine binding proteins

47
Q

What is the function of imprinting?

A

to silence chromosomal regions by DNA methylation

48
Q

What signals an end to histone methylation?

A

a boundary element

49
Q

How does methylation of cytosine proceed?

A

it is self propogating

50
Q

What role is imparted by imprinting?

A

mark a chromosome as maternal or paternal in origin

51
Q

When is an inversion loop formed?

A

during meiosis

Biochem V (11 decks)

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