Question

A goldfish is homozygous dominant for O for the gene for orange pigmented scales, but it is also homozygous for the dominant B allele of a gene that causes black scales. Any goldfish with a dominant B allele has black scales. A second goldfish is homozygous for teh recessive o allele of the orange gene and makes no orange, but it is homozygous bb at the black scale gene. This fish is white.

A. What is the genotype of the F1 from a mating between these two goldfish?

B. What is or are the phenotype(s) of the F1?

C. What relationship do the O gene and B allele have?

D. What fraction of the F@ progeny of these two fish will have orange scales when you cross F1 siblings?

Answer 1

Ans: Here allele "O" is dominant over "o". The phenotype of O is orange pigmented scales whereas o results in no orange pigmented scales.
Similarly, the B allele is dominant over b. The phenotype of B is black scales whereas b results in a white scale.
They mate two goldfishes whose genotypes are OOBB (Orange pigmented scales with black scales) and oobb (no orange with white scales).

Parents: OOBB X oobb

Gametes: OB X ob

F1 generation: OoBb (Since it has one dominant O allele, it will produce orange pigmented scales and presence of dominant B allele will produce Black scales)

Ans a. Hence the genotype of the F1 generation is: OoBb

Ans b. The phenotype of the F1 generation is Orange pigmented scales with black scales.

I hope this will help you.