Among cattle, having horns is a recessive trait. cattle without horns, which are called polled cattle, are common. suppose a horned male mated with a polled female. their offspring are all polled. on maturity, two cattle of the f1 generation mated. their offspring are a mix of polled and horned cattle. in the f2 generation, is homozygous hi dominant and is homozygous recessive. a.ppb. ppc. pp

Let say, polled (without horn) parent cattle is dominant (PP) and parent horned cattle is recessive (pp). They cross bred which produced all polled calf F1 generation. F1 will be hybrid for trait horn (Pp). On Selfing of F1 progeny ( Pp x Pp) will give  1 homozygous polled  (PP) cattle, 2 heterozygous polled (Pp) cattle and 1 cattle with horn recessive (pp) in F2 generation.

Homozygous dominant: PP recessive: pp

Explanation:

The easiest way to resolve this is by drawing Punnetts squares.

First, you know the F0 is composed of a horned male (to be horned it has to be recessive, so pp) and a polled female (this one could de PP or Pp).

All F1 results polled. If you draw Punnett's square, you'll discover to have all polled female has to be dominant PP.

pp x PP = Pp Pp pP pP = 100% Pp

The alleles of all F1 offspring will be Pp. If you cross two F1 your probabilities are:

Pp x Pp = PP Pp pP pp = 25% PP 50% Pp 25%pp

This means, 25% of the offspring have horns on F2.

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