In a diploid plant, three genes have the following map: A/a 20 m.u B/b 30 m.u C/
ID: 95367 • Letter: I
Question
In a diploid plant, three genes have the following map: A/a 20 m.u B/b 30 m.u C/c . Now there is a plant whose genotype is Abc/aBC . b. The plant whose genotype is Abc/aBC was crossed with a plant whose genotype is abc/abc. What is the ratio that the progeny whose genotype is abc/abc will occupy if there is no interference? c. The plant whose genotype is Abc/aBC crossed with a plant whose genotype is abc/abc. What is the ratio that the progeny whose genotype is abc/abc will occupy if the interference is 20%?
Explanation / Answer
b. abc/abc will occur as a result of a single cross of between A and B gene loci. In the absence of interference, the percentage recombinants is equal to the distance in mapunits between the 2 gene,
=20% = 1/5
c. The ratio of the progeny abc/abc will remain the same i.e. 1/5 . This is because interfernce is a phenomenon in which crossing over between one pair of genes would create hindrance in crossing over between the neighbouring pair and hence is relevant in case of double cross overs. The desired progeny (abc/abc) is obtained merely by a single cross over between a/A and b/B.