Question

If no crossing over is present, how many unique gametes would an individual with the genotype AaBB have after meiosis

Answer 1

In crossing over, basically genetic material is exchanged between homologous chromosomes and hence genetic variation has occurred. During meiosis, crossing over gives rise to gametes. The chromosomes are usually in pairs, one from maternal and other from the paternal side. So, basically crossing over gives rise to offspring that are genetically distinct from their parents and siblings.

However, if no crossing over occurs, the alleles of two genes on same chromosome will migrate and remain attached. There will not be exchange of genetic material taking place, and 100% genes would be paternal genes unlike in cross over during meiosis where 50% would be paternal and 50% would be recombinant one.

If crossing over would have taken place here, the number of gametes would be 2

Here, Heterozygous alleles are Aa and homozygous alleles are BB

So, since 1 pair of heterozygous allele present, 2*n, where n =number of heterozygous allele will be 2*1=2 gametes.

This would have occurred if crossing over takes place, but since crossing over does not takes place, 0 gametes would be produced because of no genetic material exchange.