Question

Think and discuss: Suppose there are two homologous chromosomes. Each chromosome contains a single mutant allele in different parts of the chromosome. How can crossovers be beneficial in this situation? (Hint: How can you create a single, mutation-free chromosome?)

Answer 1

Answer:

Cross overs can lead to formation of chromosome pairs that have no mutant allele.

Explanation:

Cross overs can lead to formation of chromosome pairs that have no mutant allele.

For example -

Suppose "X" is a mutant  allele and "x" is a mutant free allele.

Now when two homologous chromosomes contains a single mutant allele in different parts of the chromosome are crossed the following offspring are produced

X x

X XX Xx

x Xx xx

"xx" is a mutant free genotype.

Thus, crossing over can create a single mutation-free chromosome

Answer 2

Answer:

If the crossover results in the pair of the chromosome, in which one contains no mutant allele while others contain two mutant alleles.

Explanation:

• The crossing over is the genetic random recombination phenomenon in the meiosis.
• In meiosis two homologous chromosomes randomly exchange their genetic material.
• This genetic exchange can be that much random that any part of one chromosome which is near to other can be exchanged leading to lethal and beneficial mutations.
• In crossing over if one chromosome gets the mutant part of the second chromosome while other chromosome gets the normal genetic material in return. This leads to one normal chromosome and the second chromosome having two mutant alleles.