A student in a biology class crossed a male Drosophila melanogaster having a gray body and long wings with a female D. melanogaster having a black body and apterous wings. The following distribution of traits was observed in the offspring.
Phenotype Number of Offspring

Gray body, long wings 42
Gray body, apterous wings 9
Black body, apterous wings 41
Black body, Iong wings 8
Which of the following is supported by the data?

A) The alleles for gray body and long wings are dominant.
B) The alleles for gray body and long wings are recessive.
C) Genes for the two traits are located on two different chromosomes, and independent assortment occurred
D) Genes for the two traits are located close together on the same chromosome, and crossing over occurred between the two gene loci.

According to the data shown above, we can see that at the crossing of the two flies the genes for the two characteristics are located close to each other on the same chromosome, and the crossing occurred between the two genetic loci.

As you may already know, a chromosome is a molecule formed by the correlation between DNA and proteins that keep the DNA compacted and prevent it from spreading.

Genetic loci, on the other hand, are regions on chromosomes where a specific gene for a specific trait is located.