Question

The diploid number for fruit flies is 8, and the diploid number for grasshoppers is 46. If no crossing over took place, would the genetic variation among offspring from a given pair of parents be greater in fruit flies or grasshoppers? Explain.

Short answer

When there is no crossing over, there will be no formation of recombinants. The genetic variations will be higher in grasshoppers (2n is 46) when compared to fruit flies (2n is 8).

Step-by-step solution

Crossing over

Crossing over helps in bringing the recombinants, which appear very differently from parents. In mitosis, there is no crossing over; therefore, in this type of cell division, offspring are identical.

Variations in living beings

Variation in living beings is caused by mutations. If any of the nucleotide bases is altered by another one, the triplet of bases will start producing amino acid instead of the original amino acid.When there are changes in nucleotide bases of the DNA, variation occurs, and this is caused due to mutations.

A few of the other sources may bring mutation in living beings; these sources are called mutagens. Not only mutations but sexual reproduction also take part in bringing up the variations. The living beings that reproduce sexually have different offspring (these are not precisely the same to parents).

Genetic variation in grasshopper and fruit flies when there is the absence of crossing over

The sexually reproducing parents will give rise to offspring which are not clones; they are different from their parents (this is due to changes in sequences of genes).The recombination and variation are also responsible for causing changes in genes in offspring.

When there is no recombinant formation in the case of fruit flies and grasshoppers, as grasshopper has a higher number of chromosomes, this greater number of chromosomes will lead to higher variations than grasshoppers (it has less number of chromosomes).