In horses, the chestnut/cream/palomino color is determined by having two recessi

Question

In horses, the chestnut/cream/palomino color is determined by having two    recessive alleles at the extension locus. EE and Ee individuals are BLACK, ee    individuals are chestnut/cream/palomino. Chestnut vs. cream vs. palamino    color are determined by a second locus. CCHCCH individuals are chestnut,    CCHCC individuals are palamino, CCCC individuals are cream. A black horse is    crossed with another black horse. The resulting offspring is chestnut.
   a) Diagram this cross. Is this incomplete dominance? Why or why not?
   b) The two horses cross again. What is the chance that the second offspring    will be chestnut as well?

Explanation / Answer

Given that two black horses are crossed, and the resultant offspring is chestnut.

* This means that the two parents are not homozygous for the same allele. If the two parents are homozygous for the same allele, the offspring ressemble its parents

* The parents must be heterozygous to produce a different phenotype than that of both the parents.

Let the genoype of the parents be Ee. A cross between two Ee parents produce offspring in the following ratio:

EE - 25%

Ee - 50%

ee - 25%

It is not incomplete dominance. Chestnut is due to recessive allele. Presence of incomplete dominant alleles will further give rise to polaminos.

The probability is 0.25. The occurrecne of first offspring does not has effect on the second offspring, they are two independent events.

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