The fruit fly drosophila melanogaster has an allele that confers resistance to ddt and similar insecticides. laboratory strains of d. melanogaster have been established from flies collected in the wild in the 1930s (before the widespread use of insecticides) and the 1960s (after 20 years of ddt use). lab strains established in the 1930s have no alleles for ddt resistance. in lab strains established in the 1960s, the frequency of the ddt-resistance allele is 37%. which statement is correct?

a. resistance to ddt evolved in some fruit flies in order to allow them to survive
b. alloles for ddt resistance arose by mutation during the period of ddt use because of selection for pesticide resistance
c. the evolutionary fitness associated with the heritable trait of ddt resistance changed once ddt use became widespread.

B. Alleles for DDT resistance arose by mutation during the period of DDT use because of selection for pesticide resistance

Explanation:

This question boils down to the concept of GENE MUTATION. Genetic variations can arise from gene mutations or from genetic recombination (a normal process in which genetic material is rearranged as a cell is getting ready to divide). These variations often alter gene activity or protein function, which can introduce different traits in an organism.

The Biodata dated since (1930s) illustrated that the Laboratory strains of  D. melanogaster failed to prove the resistance of the organism to DDT and similar insecticides.

But, over time when the organism are being introduced to the use of DDT, the frequency of DDT resistance was 37%.

It implies that Alleles for DDT resistance arose by mutation during the period of DDT use because of selection for pesticide resistance. If a trait is advantageous and helps the individual survive and reproduce, the genetic variation is more likely to be passed to the next generation. Over time, as generations of individuals with the trait continue to reproduce, the advantageous trait becomes increasingly common in a population, making the population different than an ancestral one.

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