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Chromosomal Aberrations Flashcards

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1
Q

What are chromosomal aberrations?

A

Abnormalities in structure and number of chromosomes

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2
Q

What is meant by the term aneuploid?

A

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

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3
Q

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

A

13 patau
18 Edwards
21 down

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4
Q

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

A

Turner’s syndrome

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5
Q

What is the genotype of someone with Klinefelter syndrome?

A

XXY

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6
Q

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

A

Non-homologus end joining

Unbalanced recombination

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7
Q

Which are generally more severe: duplications or deletions?

A

Deletions

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8
Q

What is CRI-Du-Chat syndrome?

A

Arises from a deletion on chromosome 5

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9
Q

What is Di George syndrome?

A 
microdeletion on chromosome 22. Results are very variable but include:
Immunodeficiency
Hypoarathroidism
MR
cleft palate
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10
Q

What is an insertion?

A

Taking a part of one chromosome and inserting it into another

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11
Q

What is a translocation?

A

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

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12
Q

A translocation between chromosome 9 and 22 produces what disease?

A

The Philadelphia chromosome–Ber/Abl protein—chronic myeloid leukemia

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13
Q

What is a Robertsonian translocation?

A

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

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14
Q

How do inversions happen?

A

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

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15
Q

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

A

False

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16
Q

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

A

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

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17
Q

What is a balanced alteration?

A

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

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18
Q

What is an unbalanced alteration?

A

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

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19
Q

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

A

False

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20
Q

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

A

False

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21
Q

What is karyotyping?

A

Studying the composition of the chromosomes in a cell

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22
Q

What are the six indications for examining a karyotype?

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A 
Problems of early growth/development
Still birth/neonatal death
Fertility problems
Pregnancy with advanced maternal age
Cancer
Family h/o chromosomal aberrations
23
Q

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

24
Q

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

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A

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

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