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 copy, Ovov. Horses with two Ov copies, OvOv, die soon after birth and are 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 fewspot is considered fewspot 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.
overo:
leopard:
white overo:
Ovov = Overa (White splotch pattern)
OvOv = dies soon after birth
ovov = Solid colored
Lplp = Leopard phenotype (Spots everywhere)
LpLp = Fewspot phenotype (Mostly white with colored spots)
Overa + leopard = Pintaloosa (OvovLplp)
Overa + fewspot = Fewspot (OvovLpLp)
Consider the two Pintaloosa horses
OvovLpLlp x OvovLpLp
Gametes ----> OvLp Ovlp ovLp ovlp OvLp Ovlp ovLp ovlp
OvLp | Ovlp | ovLp | ovlp | |
OvLp |
OvOvLpLp |
OvOvLplp | OvovLpLp (Overa) | OvovLplp (Overa Leopard) |
Ovlp | OvOvLplp | OvOvlplp | OvovLplp (Overa Leopard) | Ovovlplp (Overa) |
ovLp | OvovLpLp (Overa Fewspot) | OvovLplp (Overa Leopard) | ovovLpLp (Solid fewspot) | ovovLplp (Solid Leopard) |
ovlp | OvovLplp (Overa Leopard) | Ovovlplp (Overa solid) | ovovLplp (solid Leopard) | ovovlplp (Solid) |
Overa: 08
Leopard: 05
White Overa: 01
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