Question

use the scenario to answer the question. there are two alleles for the gene that controls the size of wings in fruit flies. table 1 shows the two alleles and describes the phenotypes that they control. a biologist performs a cross with two fruit flies and observes the offspring that result. the results are shown in table 2 and figure 1. considering the biologist’s data, what are the most likely genotypes of the flies that are crossed?

Explanation:

Step1: Analyze the phenotype ratio

The ratio of normal - winged (49.4%) to vestigial - winged (50.6%) offspring is approximately 1:1.

Step2: Recall Mendelian genetics crosses

A cross between a heterozygous individual (Nn) and a homozygous recessive individual (nn) results in a 1:1 ratio of dominant (normal wings) to recessive (vestigial wings) phenotypes.

Step3: Evaluate each option

• Option NN x nn would result in all Nn (normal - winged) offspring.
• Option Nn x nn gives a 1:1 ratio of normal - winged (Nn) and vestigial - winged (nn) offspring.
• Option Nn x Nn gives a 3:1 ratio of normal - winged (NN + Nn) to vestigial - winged (nn) offspring.
• Option nn x nn gives all vestigial - winged (nn) offspring.

Answer:

B. Nn x nn