In a species of fish, scale color is determined by a single gene and can be red,
ID: 89114 • Letter: I
Question
In a species of fish, scale color is determined by a single gene and can be red, blue or white. To determine the relationships between the alleles, pure-breeding strains were mated to each other.
In the first generation (F1) of these crosses these were the results:
Red mated to blue gave a blue and red striped fish
Blue mated to white gave a blue and white striped fish
Red mated to white gave a red and white striped fish
A logical hypothesis that could be generated by these data is [ Select ] ["red and blue are codominant while white is recessive to both", "red is dominant to the other alleles", "the three alleles (white, red or blue) are all codominant", "blue is dominant to the other alleles"] .
If you crossed a pure breeding red strain to a blue and white striped F1 you most likely would get [ Select ] ["all the fish would be lavendar", "all blue and white striped progeny", "every fish would be tri-colored red white and blue", "equal numbers of red and white and red and blue fish", "all red progeny"]
Explanation / Answer
a) A logical hypothesis that could be generated by these data is the three alleles (white, red or blue) are all codominant.
In codominance inheritance, both the dominant and recessive traits exist together in the hybrid offspring. The offspring is neither dominant nor recessive but of a different phenotype in which both the characters are present or visible.
For example, when red (say RR) mated to blue (say BB), they produce an offspring having a different phenotype i.e blue and red striped fish (RW). This means that both traits exist together.
b) If you crossed a pure breeding red strain to a blue and white striped F1 you most likely would get equal numbers of red and white and red and blue fish.
Parents: Pure breeding red strain (RR) X blue and white striped F1 (BW)
Gametes: R B, W
Offsprings: RB (Red and blue striped fish) and RW ( Red and white striped fish)
Because all the three alleles are codominant, they will give an offspring with different phenotype in the ratio of 1:1