Question

In a three-factor cross, double crossover recombinants

a) are always the same as the parental types
b) have the same frequency as single crossovers
c) have a frequency equal to the product of the frequencies of the two single crossovers
d) are not possible

Answer 1

In a three-factor cross, double crossover recombinants have a frequency that is the product of the frequencies of two single crossovers. Double crossovers involve two separate recombination events in meiosis that generate new allele combinations different from the parental types.

Step-by-step explanation:

In a three-factor cross, double crossover recombinants have a frequency equal to the product of the frequencies of the two single crossovers (option c). This implies that the likelihood of a double crossover event occurring is the multiplication of the chances of each of the single crossovers happening independently.

These events lead to the creation of recombinants with new combinations of alleles that differ from those of the parental types. This is because during meiosis, genes that are located on the same chromosome typically stay together during inheritance; however, if they are far enough apart, crossovers can separate them and mix the alleles.