Genetic help please ! 1) In horses, WW is chestnut, Ww is palomino, and ww is white (called cremello) i) what offspring would be expected from a white stallion and palomino mare ? ii) what off...

Genetic help please !

1) In horses, WW is chestnut, Ww is palomino, and ww is white (called cremello)

i) what offspring would be expected from a white stallion and palomino mare ?

ii) what off spring would be expected from chestnut stallion and a white mare?

iii)starting with a chestnut stallion and a palomino mare, how could u go about

breeding to produce a white colt(young stallion) using only these starting animal

and their progeny?

2) In cattle, polled (hornless) (H) is dominant to horned (h), while black coat (B)

is dominant to red (b). The two gene assort independently of each other and 

is autosomal.

i) If a pure breeding line of polled black cattle was crossed with a pure breeding

breed that had horns and a red coat, what would u expect in the hybrids, and 

in the F2 produced by crossing between the F1 animals.

ii) How would the above answer change if there was a linkage between the H 

and B genes? (you could answer this by using a particular example value of the linkage

between the genes, say 20%)

3) Redishes may be long, round or or oval in shape. Crosses between long and oval gave

159 long and 156 oval. Crosses between oval and round gave 203 oval and 199 round. 

Crosses between long and round gave 576 oval, while oval by oval crosses gave 121 long,

243 oval and 119 progeny. What is the genetic control of reddish shape? Assign genotypes 

to the three phenotypes. 

Asked on by billy357

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sciftw's profile pic

sciftw | High School Teacher | (Level 1) Educator Emeritus

Posted on

I'll answer part one of your question.  You are supposed to submit separate tickets for multiple questions.  

All of question 1 is dealing with incompletely dominant genes.  It is incompletely dominant because a hybrid genotype (Ww) produces a third phenotype (palomino).  In true dominance, that heterozygous genotype would still be chestnut. 

1a.  If a white is crossed with a palomino, the expected offspring will be either white or palomino.  It will be a 50/50 expected ratio.  That's because the the palomino horse will donate the dominate gene (W) half the time and the recessive gene (w) the other half of the time.  The white horse will only donate a "w."  So the possible genotypes of the offspring can only be Ww or ww.  

1b. If you cross a chestnut (WW)  with a white (ww), the only possible offspring will be palomino.  Chestnut will always donate a dominant gene.  White will always donate a recessive.  The genotype of the offspring will always be Ww. 

1c. In order to do this one, you will need three generations.  Original parents will produce the F1.  Cross the F1 to get your desired white color. The original parents will produce a palomino 50% of the time.  Breed two of those palominos (Ww) together to get white (ww).  The only problem that I see with that cross is the unexpected results due to inbreeding. 

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