In horses, the Overo gene, Ov, produces a white splotch pattern on the coat. The

Question

In horses, the Overo gene, Ov, produces a white splotch pattern on the coat. The overo phenotype is seen only when a horse has one Ov Ovov. Horses with two copies, OvOv, die after birth and called white overo because they are completely white. Horses with no Ov copies are solid colored, ovov. The Leopard complex gene, Lp, shows incomplete dominance and controls white spotting. One Lp allele, Lplp, produces the leopard phenotype, in which there are spots everywhere. Two Lp alleles, LpLp, produce the fewspot phenotype, in which the horse is mostly white with colored spots. A horse that is both overo and leopard is called pintaloosa, and these horses are spotted with splotches. A horse that is overo and few spot is considered few spot because the white areas from Lp is indistinguishable from the white from Ov. Suppose that 16 pairs of pintaloosa horses have one offspring per pair. How many of each phenotype would be expected? Determine the number out of 16 expected for each phenotype. Only count phenotypes for offspring expected to live past one week of age.

Explanation / Answer

Hi, this is a problem involving two genes which are not linked. The inheritance is independent of each other and affects similar phenotype i.e skin coloration.

The overo phenotype = OVov ; The dead one is = OVOV ; The solid phenotype = ovov.

Leopard = LPlp ; fewspot = LPLP ;overo and fewspot = OVovLPLP = fewspot; overo-white= white

o-leopard = overpintaloose = OVovLPlp

When two pintaloose mate, they produce 16 offsprings.

OVOVLPLP

dead

OVOVLPlp

dead

OVovLPLP

fewspot

OVovLPlp

pintaloose

OVOVLPlp

dead

OVOVlplp

dead

OVovLPlp

Pintaloose

OVovlplp

Overo, white

OVovLPLP

fewspot

OVovLPlp

pintaloosa

ovovLPLP

solid, fewspot

ovovLPlp

solid, leopard

OVovLPlp

pintaloosa

OVovlplp

overo, white

ovovLPlp

solid, leopard

ovovlplp

solid white

Thus there are 16 possible types out of which 4 die soon after birth. Even if there are 16 mating pairs, each time it is the possibility of 1 among 16 different types.

4 dead out of 16.

PIntaloosa = 4 / 16

Overo white = white = 2 / 16

fewspot = 2 / 16

solid, fewpost = 1 /16

solid, leopard = 2/ 16

solid, white = 1 /1 6

OVLP OVlp ovLP ovlp OVLP

OVOVLPLP

dead

OVOVLPlp

dead

OVovLPLP

fewspot

OVovLPlp

pintaloose

OVlp

OVOVLPlp

dead

OVOVlplp

dead

OVovLPlp

Pintaloose

OVovlplp

Overo, white

ovLP

OVovLPLP

fewspot

OVovLPlp

pintaloosa

ovovLPLP

solid, fewspot

ovovLPlp

solid, leopard

ovlp

OVovLPlp

pintaloosa

OVovlplp

overo, white

ovovLPlp

solid, leopard

ovovlplp

solid white

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