Basic body color for horses is influenced by several genes, one of which has several different alleles. Two of these alleles— the chestnut (dark brown) allele and a diluting (pale cream) allele (often incorrectly called albino)—display incomplete dominance. A horse heterozygous for these two alleles is a palomino (golden body color with flaxen mane and tail). Is it possible to produce a herd of pure-breeding palomino horses? Why or why not? Work the Punnett square for mating a palomino to a palomino and predict the phenotypic ratio among their offspring.

Explanation:

 As given:

The chestnut (dark brown) allele and a diluting (pale cream) alleles show incomplete dominance, means that both the alleles in heterozygous condition show their effect. So the heterozygous show the phenotype which is intermediate of both the parents, here a horse heterozygous for these two alleles is a palomino.

 There is in fact, no particular allele present for palomino, this phenotype only results due  to having two  different alleles for a gene. So, palominos can never be pure-breeding because they can never be  homozygous.

Let P1 chestnut and P2  dilute,

Palomino is P1P2

The Punnett’s  Square for palomino mated to palomino:

P1P2×  P1P2

Gametes are: parent-1 P1 and  P2 , parent-2:  P 1  and P2

Progeny are:  P1P1,      P1P 2,    P 2 P1,    P2 P2

Genotypic Ratio: 1 P1P 1  : 2 P1P 2  : 1 P2P 2

Phenotypic Ratio: 1 Chestnut : 2 Palomino : 1 Dilute

the scientific method.