One polled (hornless) bull is bred to 3 cows. With Cow A, which is horned, a polled calf is produced. With Cow B, also horned, a horned calf is produced. With Cow C, which is polled, a horned calf is produced. What are the genotypes of the bull and the 3 cows

Bull = Pp

Cow A = pp

Cow B = pp

Cow C = Pp

Explanation:

In cows polled (P) is dominant over horned (p) trait.

The bull is polled so it can be PP or Pp. Cow B is horned so it must be pp. Resultant offspring from bull X Cow B is also a horned calf (pp). This calf must have received one p from the bull. So the bull's genotype is Pp.

Cow A is also a horned cow so it must be pp. When bull X Cow A, a polled calf is produced. Since the bull's genotype is Pp and Cow A's genotype is pp, this polled calf will be Pp like the bull.

Cow C is polled like the bull so it can be PP or Pp. However on crossing with the bull (Pp) a horned calf is produced (pp). This calf got one p allele from the bull and p allele from the Cow C. So Cow C's genotype must be Pp.

Hence,

Bull = Pp

Cow A = pp

Cow B = pp

Cow C = Pp

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.

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