Chromosomal Abnormalities

Question 1

What is a human karyotype?

Answer 1

A picture of a cell’s complete set of chromosomes grouped together in pairs and arranged in order of decreasing size

Question 2

How is it obtained?

Answer 2

Process involving Venous blood / Amniotic cells and CVS.
Use white cells, stop during metaphase (Commonly now prophase)
Use stain and place on slide

Question 3

Ideogram

Answer 3

Show structural feature

Question 4

p-arm? short or long

Answer 4

Short (petite)

Question 5

What does 47, XX +21

Answer 5

47 total number of chromosome, XX denotes the sex of the individual, +21 . Means the extra chromosome is chromosome 21.

Question 6

Heterochromatin (dark) on ideogram

Answer 6

More compact (fewer genes)

Question 7

Euchromatin (light) on ideogram

Answer 7

More open (more genes)

Question 8

What is non-disjuncture?

Answer 8

Result in uneven number of chromosomes occurs during meiosis.
Causes Trisomy and monosomy

Question 9

What is the most common aneuploidy? Why is there tolerance?

Answer 9

Sex chromosomes tolerance as often X inactivation in females and y gene in males are in a low content.

Question 10

When can sex aneuploidy become a problem?

Answer 10

pseudoautosomal region. i.e. even when some genes remain active even if the chromosome is inactivated.

Question 11

What are the three abnormalities of chromosome structure?

Answer 11

Numerical
Structural
Mosaicism

Question 12

What are Single chromosome abnormalities?

Answer 12

Inversion of a gene, duplication and deletion of a gene

Question 13

What are two chromosome abnormalities?

Answer 13

Translocation

Question 14

What is mosaicism?

Answer 14

Presence of two or more populations of cells with different genotypes. Mild phenotype

Question 15

What are numerical abnormalities and why is caused?

Answer 15

Monsomy,
Trisomy
Non-dysjunction

Question 16

What are the structural abnormalities?

Answer 16

Insertion,
Duplication,
Inversion,
Translocation
Robertsonian translocation