In viruses called retroviruses, the genetic information is contained in RNA; these viruses have no DNA. These viruses also have an enzyme called reverse transcriptase. What is its function?

It catalyses the synthesis of complementary DNA copies from RNA.

Explanation:

The reverse transcriptase is an enzyme that allows strands of DNA molecules to be synthesized from a single strand RNA template. The enzyme, also known as RNA directed DNA polymerase is usually used by retroviruses to synthesize complementary DNA sequence from an RNA template, a process that is an opposite of transcription.

b is dominant over the allele for the white fur.