It has been proposed that insect pests could be controlled by introducing transl

Question

It has been proposed that insect pests could be controlled by introducing translocations into wild populations. According to the proposal, 50% of the offspring of crosses between wild-type insects and insects carrying the translocation (as heterozygotes) would die.

Assume that the parents have the same chromosomes involved in the translocations and that the translocation breakpoints are not lethal. Also assume that for the translocation chromosomes involved, chromosomes with homologous centromeres never segregate together during meiosis.

What proportion of the progeny of crosses between two such translocation-carrying insects would die?

Enter your answer as a reduced fraction.

Explanation / Answer

After translocation unbalanced meiotic products are formed. Suppose the genotype of wild type parent is AABB; which will produce the gametes AB.

The genotype of translocated parent cell will be AA'BB'. A' is the chromosome having translocated portion from B. and B' is the chromosome having translocated portion from A. The gametes produced from such a parent will be AB, A'B', A'B and AB'. Chances of having AA = 1/2 and chances of having BB is also 1/2. AABB and AA'BB' will be normal. Total chance of having normal offspring becomes 1/2

Crossing AA'BB' with AA'BB' will give AABB, AA'BB' and A'A'B'B' normal offsprings. Chances of having AA' = 1/2. Chances of having BB'= 1/2.

Chances of having AA'BB' = 1/2 *1/2=1/4= 4/16.

Chances of having AABB= 1/16

Chances of having A'A'B'B' = 1/16

Total normal offsprings = 4+1+1/16= 6?16

Total number of normal offsprings which will be living is 6/16

So, 10/16 offsprings of two such translocation-carrying insects would die..

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