Question

Fluffernutter labradors are identical to Earth labradors in every way, except that they grow marshmallows instead of fur. The three possible types of marshmallow skin are: a. Black (tastes like licorice); b. Chocolate (tastes like chocolate); c. Yellow (tastes like vanilla). There are two genes that control for this phenotype, acting in a recessive epistatic manner. The two-locus genotypes that correspond to the phenotypes are:

Answer 1

Alleles at the two genes/loci:

- Locus 01: A (dominant), a (recessive)

- Locus 02: B (dominant), b (recessive)

A_B_ (Licorice)

aaB_ (Chocolate)

__bb (Vanilla)

Step-by-step explanation:

Recessive epistasis is the genetic interaction phenomenon where recessive alleles at one locus mask the phenotypic expression of another gene locus. In a recessive epistatic interaction between two genes, the phenotypic ratio of the three resulting phenotypes is 9: 3: 4. In this case, there are two genes responsible for the three phenotypes Licorice, Chocolate, and Vanilla. One locus is responsible for determining if Fluffernutter labradors will be Licorice or Chocolate. Licorice is dominant and will be expressed if the Fluffernutter labrador has a AA or Aa, while Chocolate is recessive and therefore it is expressed only in aa Fluffernutter labradors. However, the expression of the phenotype is determined by another gene pairing. The epistatic allele b in homo-zygous condition will produce Fluffernutter labradors with Vanilla phenotype.