In cats fur colour can be black, orange or tortoise (patched orange and black). A mating
between two cats produces the kittens indicated below.
P: tortoise female X orange male
F1: orange females
tortoise females
black males
orange males
What are the genotypes of the parents and F1 progeny, if fur colour is controlled by X-linked
alleles?
The fact that fur colour can be tortoise means that both phenotypes are expressed, as a result of codominance of the genotypes black and orange.
Since we are given that fur colour is controlled by X-linked alleles, it means that tortoise can only be inherited in females (XX) where there are two X-alleles. In males (XY), the only X-allele will control the fur colour, namely black or orange.
If
O=orange
B=black
Y=Y-allele (from male only), irrelevant in fur colour.
Then the male parent is OY (orange), and the female parent is OB (tortoise).
Resulting in F1 as
OY (orange male)
BY (black male)
OB (tortoise female)
OO (orange female)
exactly as given in the question above.
To determine the genotypes of the parents and F1 progeny, we need to understand how fur color is controlled by X-linked alleles. In this case, let's assign the following alleles:
- B: Black fur color allele
- O: Orange fur color allele
- T: Tortoise (patched orange and black) fur color allele
From the given information, we know that the mother (P) is tortoise and the father (P) is orange. Since fur color is controlled by X-linked alleles, let's assume that the mother has two X chromosomes (XX) and the father has an X and Y chromosome (XY).
Now let's determine the genotypes of the parents:
- The tortoise female (XX) will have the genotype XT, meaning she has one X chromosome with the tortoise allele and another X chromosome with either the orange or black allele.
- The orange male (XY) will have the genotype XO, meaning he has one X chromosome with the orange allele and a Y chromosome.
Next, let's determine the possible genotypes of the F1 progeny:
- Orange females: Since the mother is tortoise (XT) and the father is orange (XO), the F1 orange females must inherit an X chromosome from the father with the orange allele (XO). Thus, their genotypes would be XO.
- Tortoise females: The mother is tortoise (XT), so the F1 tortoise females must inherit an X chromosome from the mother with the tortoise allele (XT). Thus, their genotypes would be XT.
- Black males: The mother is tortoise (XT), so the F1 black males must inherit an X chromosome from the mother with the black allele (XB). Thus, their genotypes would be XB.
- Orange males: The father is orange (XO), so the F1 orange males must inherit an X chromosome from the father with the orange allele (XO). Thus, their genotypes would be XO.
In summary:
- The mother's genotype is XT.
- The father's genotype is XO.
- The genotypes of the F1 progeny are as follows:
- Orange females: XO
- Tortoise females: XT
- Black males: XB
- Orange males: XO