Chromosomal Aberrations Flashcards Preview

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Flashcards in Chromosomal Aberrations Deck (53):
1

What are chromosomal aberrations?

Abnormalities in structure and number of chromosomes

2

What is meant by the term aneuploid?

uneven number of chromosomes (e.g. 1 or 3)

3

What are the three trismonies that can be observed in practice?

13 patau
18 Edwards
21 down

4

A person with only one X chromosome and no Y has what syndrome?

Turner's syndrome

5

What is the genotype of someone with Klinefelter syndrome?

XXY

6

What are the two ways in which structural chromosomal abnormalities occur?

Non-homologus end joining
Unbalanced recombination

7

Which are generally more severe: duplications or deletions?

Deletions

8

What is CRI-Du-Chat syndrome?

Arises from a deletion on chromosome 5

9

What is Di George syndrome?

microdeletion on chromosome 22. Results are very variable but include:
Immunodeficiency
Hypoarathroidism
MR
cleft palate

10

What is an insertion?

Taking a part of one chromosome and inserting it into another

11

What is a translocation?

Taking a part of one chromosome and attaching it onto the end of another

12

A translocation between chromosome 9 and 22 produces what disease?

The Philadelphia chromosome--Ber/Abl protein---chronic myeloid leukemia

13

What is a Robertsonian translocation?

When two chromosomes simultaneously exchange material via translocation. Results in the longs pairing, and the shorts pairing

14

How do inversions happen?

When a chromosome is damaged and the broken fragment is attached upside down

15

True or false: inversions of chromosomes are almost always lethal for the carrier.

False

16

True or false: inversions of chromosomes are almost always lethal for the carrier's offspring. Why/why not?

True, because the inverted regions have to loop around in meiosis to pair with the homologous chromosome. If crossover occurs, then this is a translocation

17

What is a balanced alteration?

A chromosomal rearrangement that does not change the amount of DNA in the affected cell

18

What is an unbalanced alteration?

A chromosomal rearrangement that changes the amount of DNA in the affected cell

19

True or false: carriers of balanced alterations are usually aware of their condition?

False

20

True or false: carriers of balanced alteration usually produce viable offspring

False

21

What is karyotyping?

Studying the composition of the chromosomes in a cell

22

What are the six indications for examining a karyotype?

Problems of early growth/development
Still birth/neonatal death
Fertility problems
Pregnancy with advanced maternal age
Cancer
Family h/o chromosomal aberrations

23

Out of 10000 pregnancies, how many live births are there? Spontaneous abortions?

8500, 1500

24

Out of 10000 pregnancies, how many will have normal chromosome? Abnormal?

9200 normal (92%), 800 abnormal

25

Of the 8500 live births, how many children will have down syndrome?

10

26

A deletion of chromosome 5 results in what disease? Symptoms?

Cri-du-chat syndrome. MR, microcephaly, micrognathia, heat defects, cat-like-cry

27

A microdeletion on chromosome 22 results in what disease? Symptoms?

Di George syndrome. Congenital heart defects, MR, cleft palate, immunodeficiency

28

A traslocation between chromosome 9 and 22 produces what disease/new chromosome?

Philadelphia chromosome produced, chronic myeloid leukemia due to overexpression of Abl1 gene due to translocation to Bcr. (Abl/Br tyrosine kinase)

29

What type of crossover occurs when two entire arms are switched?

Robertsonian translocation

30

What is the term that describes the translocation of a chromosome and a reinsertion of the gene backwards? When is this a problem?

Inversion
Problem for individual's offspring, not usually individual them self.

31

What are the three things to look for in a pedigree that is suggestive of chromosomal inheritance?

1. MR, multiple symptoms
2. Multiple spontaneous abortions
3. infertility

32

How do chromosomal abberrations result in CA?

Genomne instability deletes tumor suppressors/ amplifies oncogenes

Loss of cell cycle control

33

What is the karyotype for Turner's syndrome?

45, X

34

What is the karyotype for Klinefelter syndrome?

47, XXY

35

What is the karyotype for Edwards, patau, and down syndomes?

47, 13 = Patau
47, 18 = Edwards
47, 21 = Down

36

Of 10000 pregnancies, how many balanced rearrangements will there be? How many of these will spontaneously abort? How many survive?

19/10000 pregnancies
3/19 die
16 survive

37

Of 10000 pregnancies, how many unbalanced rearrangements will there be? How many of these will spontaneously abort? How many survive?

27/10000 pregnancies
23 die
4 survive

38

Of 10000 pregnancies, how many will have normal chromosomes? How many of these will spontaneously abort? How many survive?

9200/10000 will have normal chromosomes
750 die
8450 survive

39

Of 10000 pregnancies, how many will have ABnormal chromosomes? How many of these will spontaneously abort? How many survive?

800/10000 will have abnormal chromosomes
750 die
50 survive

40

Of 10000 pregnancies, how many will have extra X chromosomes? How many of these will spontaneously abort? How many survive?

19/10000 pregnancies
4 die
15 survive

41

Of 10000 pregnancies, how many will have Down syndrome? How many of these will spontaneously abort? How many survive?

45/10000 pregnancies
35 die
10 survive

42

What percentage of children are born with recognizable birth defects?

2-3%

43

What is the rate of child death due to birth defects? To premature birth?

20% 20%

44

Give data for HPNOC (my acronym)?

Heart defects 1/100-1/200
Pyloric stenosos 1/300
Neural tube defects 1/1000
Orofacial clefts 1/700 - 1/1000
Clubfoot 1/1000

45

What percent of birth defects have complex inheritance?

50%

46

What percent of births are caused by single chromosomal defects?

25%

47

What percent of birth defects are caused by single GENE mutations?

20%

48

What percent of birth defects are caused by non-genetic factors?

5%

49

Chromosomal and genomic disorders affect what percent of the population?

0.38%

50

Single gene disorders affect what percent of the population?

2%

51

Disorders with multifactorial inheritance affect what percent of the population?

60%

52

What is the prevalence of Down? Edward? Patau?

1/800 for Down
1/8000 for Edward
1/25000 for patau

53

What is the prevalence of Turner syndrome?

1/2500