Chromosomal Aberrations

Question 1

Give the frequency of chromosomal aberrations, @ conception and birth

Answer 1

Abnormal: 800/10000, at birth: 50/10000

Trisomy 21: 45 — 10
Sex Chrom: 19 — 15

Unbalanced 27 4
Balanced 19 16

Question 2

Name the 2 sources for mutations affecting chrom structure.

Answer 2

1. NHEJ: create chimeric chromosomes when they heal DNA double stranded breaks
2. Unbalanced recombination: causes deletions and duplications

Question 3

Balanced vs Unbalanced

Answer 3

Balanced: no loss of DNA; due to insertion or translocation
(mom is usually a carrier and will not have symptoms but will affect offspring)

Unbalanced: results in loss or gain of DNA due to deletion or duplication

Question 4

Cri-du-chat vs Di George Syndrome

Answer 4

Cri-du-chat: del5p: cat-like cry; mental problems,

Di George Syndrome: del22q; immunodeficieny, hypoandro, heart problems

Question 5

Trisomy 21
Trisomy 18
Trisomy 13

Answer 5

Down, Edwards, Patau

Question 6

What is Klinefelter?

Turner?

Answer 6

47 XXY male

45 X female

Question 7

Philadelphia Chromosome

Answer 7

translocation in 9 to 22; leading to BCR-ABL (functions as a dominant oncogene), which results in chronic myeloid leukemia

Question 8

Robertsonian Translocation

Answer 8

13q and 14q translocation: results in gametes with balanced or unbalanced abberations

most common rearrangement: 1/1300

Question 9

Explain the mitotic problems arising with inversion?

Answer 9

results when a chromosome suffers 2 breaks and the broken off fragment is reinserted int eh wrong orientation. Problems can arise in offspring. If cross over occurs, chrom material is translocated and gametes are inviable.

Question 10

Explain the rationale for karyotyping? (6 reasons)

Answer 10

1. problems in early growth/development
2. stillbirth/neonatal death
3. fertility problems
4. pregnancy at advanced maternal age
5. cancer
6. family history of chrom aberratoins

Question 11

How do you perform a karyotype?

Answer 11

culture lymphocytes from blood’ arresting the cells in metaphase and lysing;

Perform FISH to identity chromosomes

Question 12

Describe 3 things that suggest of chrom inheritance?

Answer 12

1. cause multiple abnormalities
2. cause spontaneous abortions/miscarriages
3. infertility

Question 13

Genomic instability contributes to the progression of cancer by doing what 2 thigns?

Answer 13

amplifying oncogenes and deleting tumor supressor genes