In Dexter and Kerry cattle animals may be polled hornless or

In Dexter and Kerry cattle, animals may be polled (hornless) or horned. The Dexter animals have short legs, whereas Kerry animals have long legs. When many offsprings were obtained from matings between polled Kerrys and horned Dexters, half were found to be polled Dexters and half polled Kerrys. When these two types of F1 cattle were mated to one another, the following F2 data were obtained:

3/8 polled Dexters

3/8 polled Kerrys

1/8 horned Dexters

1/8 horned Kerrys

A geneticist was puzzled by these data and interviewed farmers who had bred these cattle for decades. She learned that Kerrys were true breeding. Dexters, on the other hand, were not true breeding and never produced as many offsprings as Kerrys. Based on this, what will be the result from a mating between two F1 polled Dexters?

Solution

we first need to assume the genotypes : polled P would be dominant to p horned. and smilarly short legs or dexter would be dominant L and kelly or long legs is recessive l.

it says that kerry is true breeding so it would be : polled kerry : PPll and horned dexter would be ppLl

when we cross it, we get :

we get polled dexter which is PpLl and polled kerry Ppll.

when we will cross these we would get the ratio of :

3/8 polled Dexters

3/8 polled Kerrys

1/8 horned Dexters

1/8 horned Kerrys.

hence the polled dexter in F1 were PpLl. when we cross it, we get the 4 gametes each : PL, Pl, pL, pl and the cross is as follows:

the phenotypic ratio is 9:3:3:1

polled dexter, polled kerry, horned dexter, horned kerry.