Chromosomal Aberrations Flashcards Preview

Biochem V > Chromosomal Aberrations > Flashcards

Flashcards in Chromosomal Aberrations Deck (51):
1

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

0.2%

0.5%

2

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

healing of DNA by double stranded breaks

unbalanced recombination

3

How does Cri-du-chat arise?

deletion on chromosome 5

4

What is DiGeorge syndrome also known as?

velocardiofacial syndrome

5

How does DiGeorge syndrome arise?

microdeletion on chromosome 22

6

What is the mode of inheritance for DiGeorge Syndrome?

autosomal dominant

7

Where does a translocation insert a chromosome? Insertion?

end of another chromosome

insertion = middle

8

What happens in a Robertsonian translocation?

long and short arms of a chromosome are exchanged

9

What is the most common chromosomal aberration in humans?

Robertsonian translocation

10

Which chromosomes are often involved in a Robertsonian translocation?

13q and 14q

11

What is an inversion?

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

12

What is a balanced chromosomal rearrangment?

no change in the amount of genetic material

13

What can nondisjunction in meiosis lead to?

cells with surplus or missing chromosomes

14

What are the two processes that generate structural chromosomal aberrations?

non-homologous end joining and

15

What is more severe, deletions or duplications?

deletions

16

How does Cru du Chat arise?

deletion on chromosome 5

17

How does diGeorge syndrome arise?

microdeletion on chromosome 22

18

What is DiGeorge syndrome also known as?

velocardiofacial syndrome

19

What is the most common phenotype of DiGeorge syndrome?

congenital heart defect

20

Where does an insertion move a chromosome?

into the middle of another chromosome

21

What does a translocation move a chromosome?

attaches it to the end

22

How is the Philadelphia Chromosome generated?

a translocation between chromosome 9 and 22

23

Regarding the Philadelphia Chromosome, what specific genes are traslocated?

ABL tyrosine kinase from 9 to the BCR region on 22

24

What is a Robertsonian translocation?

long and short arm of two chromosomes are exchanged

25

What is the most common chromosomal rearrangement?

Robertsonian Translocation of 13q and 14q

26

What is an inversion?

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

27

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

an inversion loop is created

28

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

it gets lost

29

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

ABL from 9 moves to BCR of 22

30

A robertsonian translocation often involves which two chromosomes?

13q and 14q

31

What will an inverted chromosome form in meiosis?

inversion loop

32

Regarding an inversion loop, what can meiosis create?

a dicentric or acentric chromosome

33

When do patients usually become aware of their balanced translocation?

reproduction

34

What cells is most frequently used to perform karyotypes?

lymphocytes

35

What cell cycle phase are chromosomes arrested in during karyotyping?

metaphase

36

Where does methylation of DNA occur?

on cytosine residues in CpG islands

37

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

DNMT 3a and 3b

38

What protein is defective in Rett Syndrome?

methyl cytosine binding protein

39

What characteristic of DNA is lost during Rett Syndrome?

Loss of txn silencing

40

How is Rett Disease transmitted?

X-linked dominant

41

Where does the silencing of histones occur via acetylation?

tail

42

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

phosphorylation, ubiquitination and methylation

43

What protein binds methylated histones?

HP1

44

What happens to histones after they are deacetylated?

they become methylated

45

What do HP1 proteins bind?

histone methylase

46

What are MBPs?

methylcytosine binding proteins

47

What is the function of imprinting?

to silence chromosomal regions by DNA methylation

48

What signals an end to histone methylation?

a boundary element

49

How does methylation of cytosine proceed?

it is self propogating

50

What role is imparted by imprinting?

mark a chromosome as maternal or paternal in origin

51

When is an inversion loop formed?

during meiosis