Question

You are engaged in a project to breed new color variants in snakes. A certain chromosome carries three genes that all affect pigmentation. Two of the genes, A and B are near each other on the chromosome, but gene C is further away. You are hoping to maintain the versions of the three genes from the maternal chromosomes in some of the grandchildren. What would you predict for the behavior of these genes during crossover in meiosis?
A. All three genes are equally likely to be separated by a crossover event, since these are randomly distributed.
B. The maternal chromosome will be transmitted as it is to half of the progeny.
C. The maternal chromosome will be transmitted as it is to all of the progeny.
D. Genes A and B are likely to stay together, but they are more likely to become separated from gene C since a crossover is more likely to occur in the longer space between them.

Answer 1

Answer:

D. Genes A and B are likely to stay together, but they are more likely to become separated from gene C since a crossover is more likely to occur in the longer space between them.

Explanation:

Cross over between homologous chromosomes occurs during meiosis I. A synapsis is formed and non sister chromatids exchange genetic material between each other. If gene A and gene B are close to each other on a chromosome, they most likely will show linkage. During cross over these genes will have more probability to get inherited together from the parent and hence offspring with parental combination will be more in number. Since gene C is farther away from the two genes, it will show normal cross over and recombination. Offspring produced will have almost equal parental and new combination.