Question

Why is a 50% recovery of single-crossover products the upper limit, even when crossing over always occurs between 2 linked genes?

A) The probability of double crossovers increases.
B) Single crossovers are less likely to occur between linked genes.
C) The DNA is damaged during crossing over.
D) The genes are physically linked on the same chromosome.

Answer 1

A 50% recovery of single-crossover products is the upper limit for linked genes on the same chromosome because each gamete can only inherit one set of linked genes, and due to the possibility of multiple crossovers, not all products will be single-crossover types.

Step-by-step explanation:

The reason that a 50% recovery of single-crossover products is the upper limit, even when crossing over always occurs between 2 linked genes, relates to the physical linkage of genes on the same chromosome. When two genes are linked, they are situated on the same chromosome, which carries important implications for genetic inheritance and variation.

When genes are far apart on the chromosome, it is true that crossovers are likely to occur every meiotic division; however, the potential for double crossovers or other combinations of crossing over means that not all meiotic products will be single-crossover types. Often, what appears to be a non-crossover gamete may actually be the product of two crossovers.