Question

which of the following likely does not reflect the presence of one or more gene mutations?
multiple choice
fruit flies subjected to intense radiation produce a wider array of variable offspring.
a chemical leaking from the surface of an old abandoned coal mine alters a regulatory gene so that a cricket nymph develops an extra set of eyes.
the average body size of individuals in a population is smaller in a drought year than in a year with normal rainfall.
the bacteria that cause gonorrhea, a common sexually transmitted disease, have previously been killed by penicillin; however, after continuous usage of the antibiotic, penicillin - resistant strains are now becoming prevalent.

Explanation:

Gene mutations are changes in the DNA sequence. Fruit - flies exposed to radiation, a chemical altering a gene in a cricket, and bacteria developing antibiotic - resistance are all examples of gene mutations. However, the change in average body size of a population due to drought is likely a phenotypic change due to environmental factors (phenotypic plasticity) rather than a gene mutation.

Answer:

The average body size of individuals in a population is smaller in a drought year than in a year with normal rainfall.