Lecture 7: Cytogenomics

Question 1

What is a chromosome?

Answer 1

1 molecule of DNA compacted together as a result of Protein-DNA interactions

Question 2

The p arm is _______ the q arm is _______

Answer 2

Short

Long

Question 3

What is a metacentric chromosome?

Answer 3

The centromere is positioned so the p arm is almost as long as the q

Question 4

What is a submetacentric chromosome?

Answer 4

The centromere is positioned so the p arm is definitely shorter than the q arm

Question 5

What is an acrocentric chromosome?

Answer 5

The centromere is positioned so short it’s hard to observe (satellite region)

Question 6

What are the 2 types of chromosome abnormalities?

Answer 6

Numerical: extra or missing chromosomes
Structural: abnormal structure

Question 7

What causes numerical errors?

Answer 7

Faulty cell division or fertilisation errors

Question 8

What is a euploid abnormality?

Answer 8

A disorder with multiples of the haploid set i.e. triploidy (3 of each chromosome), tetraploidy (4 of each chromosome)

Question 9

What is an aneuploidy abnormality?

Answer 9

A disorder where there is gain or loss of one or more chromosomes

Question 10

What causes structural abnormalities?

Answer 10

Translocations, Insertions, Deletions etc.

Question 11

What is a balanced structural abnormality?

Answer 11

There is no net gain/loss of genetic material

Question 12

What is an unbalanced structural abnormality?

Answer 12

There is a net gain/loss of genetic material

Question 13

What are Robertsonian translocations?

Answer 13

A balanced translocation between 2 acrocentric chromosomes.

Question 14

What is a reciprocal translocation?

Answer 14

The balanced exchange of genetic material between 2 non-homologous chromosomes

Question 15

Are insertions balanced?

Answer 15

Yes as long as there is no net gain/loss of material

Question 16

Are inversions balanced?

Answer 16

Yes

Question 17

Are deletions balanced?

Answer 17

No

Question 18

Are duplications balanced?

Answer 18

No

Question 19

What is a terminal deletion/duplication?

Answer 19

A deletion/duplication that occurs at the extremes of the chromosomes (on the ends not attached to the centromere)

Question 20

What is an interstitial deletion/duplication?

Answer 20

A deletion/duplication that occurs in the middle of either arm on the chromosomes

Question 21

What are the clinical impacts of cytogenomic variants?

Answer 21

No apparent effect (balanced or mosaic)
Reproductive issues (structural)
Apparent effects (unbalanced)

Question 22

What are isochromosomes?

Answer 22

Instead of normal separation of sister chromatids, the 2 short arms separate together and the 2 long arms separate together (unbalanced)

Question 23

What is mosaicism?

Answer 23

Presence of cell lines with different chromosomal constitutions in the same individual (can be numerical or structural changes)