A quarter horse breeder wishes to test her award winning black, smooth-haired st

Question

A quarter horse breeder wishes to test her award winning black, smooth-haired stallion to determine if he carries the recessive gene for curly hair. Assume she has access to:

- 4 recessive homozygous curly haired mares

-14 known carrier mates

-15 daughters of the stallion

-A population of 35 mares with the frequency of curly hair of 0.1

a). Estimate the probability of detection for each of the above cases. Which group was the "best" for detection?

b). Which group would be the "best" if it was also thought that the stallion was a carrier of chestnut color (chestnut is recessive to black)? Why?

Explanation / Answer

Answer a: We can detect whether the stallion is a carrier or not by using options 1 and 2.

In case of option a if the stallion is a carrier and is allowed to mate with one of the recessive homozygous curly haired mares, then the cross would be Ss x ss. A monohybrid cross result shows 50% chance of the next progeny having curly hair.  

In case of option b if the stallion is a carrier and is allowed to mate with the carrier mate, then the cross would be Ss X Ss. A monohybrid cross result shows 25% chance of the next progeny having curly hair.  

The option c would be helpful if the allele was sex linked and the option d helps us to get an idea of the population genetics on the whole but both are not useful in the given problem.

Answer b: The option b would be the best option because we can mate the stallion with one of the carrier of chestnut colour. A monohybrid cross result shows 25% chance of the next progeny having chestnut colour.

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