Structural Aberrations: Deletions and Ring Chromosome

Question 1

This refers to a loss of any part of a chromosome.

Answer 1

Deletion

Question 2

Deletions arise from:

Answer 2

loss of a portion of the chromosome between two breakpoints (interstitial deletions)

as a result of unequal crossing-over

as a result of a parental translocation

as a terminal deletion.

Question 3

In terminal deletion, the deletion continues proximally until a DNA region homologous to telomere sequences is reached. Here, the enzyme _____ is able to synthesise a new telomere and so arrest the deletion.

Answer 3

telomerase

Question 3

T/F. In terminal deletion, the deleted portion lacks a centromere (an acentric fragment) and will be lost at a subsequent cell division.

Answer 3

True

Question 3

If the ring has a centromere, then it may be able to pass through cell division. A sister chromatid exchange within a ring results in a ___ ring of ____ the size in subsequent divisions

Answer 3

dicentric; twice

Question 4

This arises from breaks in both arms of a chromosome: the terminal ends are lost and the two proximal sticky ends unite to form a ring.

Answer 4

Ring chromosome

Question 5

Deletions of a size close to the limit of resolution with the light microscope are termed _____ and molecular techniques have been developed to aid their detection

Answer 5

microdeletions