Structural Aberration: Translocation

Question 1

____ is the transfer of chromosomal material between chromosomes.

Answer 1

Translocation

Question 2

In a _____, chromosomal material distal to breaks in two chromosomes is exchanged.

Answer 2

reciprocal translocation

Question 2

In the liveborn offspring of the carrier of balanced translocations, one would expect a ratio of ____.

Answer 2

1 normal : 1 balanced : 4 unbalanced.

Question 2

In individuals with translocation are usually clinically normal and is said to have a ____.

Answer 2

balanced translocation

Question 3

T/F. Translocation exchanges usually results in no significant loss of DNA and no gene disruption.

Answer 3

True.

Question 4

T/F. The medical significance of translocation is for future generations, because a balanced translocation carrier is at risk of producing chromosomally unbalanced offspring.

Answer 4

True.

Question 5

Three types of translocation are recognised. These are…

Answer 5

Reciproca
Robertsonian (centric fusion)
Insertional.

Question 6

T/F. Visible imbalance involves large numbers of genes, and affected conceptions may miscarry, or, if liveborn, learning disability and multiple congenital malformations would be found.

Answer 6

True.

Question 7

_____ arise from breaks at or near the centromere in two acrocentric chromosomes with cross-fusion of the products.

Answer 7

Robertsonian translocations

Question 8

T/F. An acentric fragment cannot undergo mitosis and will usually be lost at a subsequent cell division.

Answer 8

T

Question 8

What is the most likely cause of Robertsonian translocation?

Answer 8

NAHR occurring at homologous sequences within the acrocentric short arms during first meiosis

Question 8

For particular translocations, unbalanced offspring produced by a ____ segregation may be viable, e.g. with partial triplication of chromosome ____ and ____.

Answer 8

three-to-one; 11 and 22

Question 9

In most cases, the breaks are just above the centromere and so the products are a single chromosome with two centromeres, _____ and a fragment with no centromere, _____ bearing both satellites.

Answer 9

dicentric; acentric

Question 10

Centric fusion of chromosomes ____ is the single most frequent type of translocation in humans, and this is followed in frequency by centric fusion of ____.

Answer 10

13 and 14; 14 and 21

Question 11

If insertional translocation involves two chromosomes, this results in _____ of a segment of one, which is inserted into the gap in the other

Answer 11

interstitial deletion

Question 11

T/F. In insertional deletion, the balanced carrier is healthy but may produce unbalanced offspring with either a duplication or a deletion, but not both.

Answer 11

True

Question 11

In Robertsonian translocation, individual is healthy, but problems may arise at gametogenesis. When the chromosomes pair during meiosis a ____ is formed, which allows homologous segments to be in contact.

Answer 11

trivalent

Question 12

In this type of translocation, three breaks are required in one or two chromosomes.

Answer 12

insertional translocation