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Genetics punnet square, sex lethal etc

In sheep the polled condition ( hornless ) is controlled by a single gene locus with two alleles. Heterozygous females are polled but heterozygous males have horns. Suppose two Heterozygous sheep were crossed. Refer to attachment for multiple choice questions.

In sheep the polled condition ( hornless ) is controlled by a single gene locus with two alleles. Heterozygous females are polled but heterozygous males have horns. Suppose two Heterozygous sheep were crossed.

1. What fraction of the male progeny will have horns ?
a. none
b. ¼
c. ½
d. ¾
e. all

2. What fraction of the female progeny will have horns ?
a. none
b. ¼
c. ½
d. ¾
e. all

3. This is an example of
a. sex influenced inheritance
b. sex limited inheritance
c. sex linked inheritance
d. sex dominant inheritance
e. sex conditioned inheritance

Suppose a geneticist made the following cross involving the two mutants at the sex-lethal locus that we discussed in class:

SxlF / SxlM X SxlF / >

1. What percentage of the progeny will survive to adulthood ?
a. 0%
b. 25%
c. 50%
d. 75%
e. 100%

The first mutant discovered in Drosophila was the X-linked recessive white eye (w). Since them several other alleles of white have been discovered including one that has an apricot eye color (wa). wa is recessive to wild type. The heterozygote w / wa has a pale orange eye color.

Suppose the following cross was made :

w+ / wa female X w / > male

1. What fraction of the male progeny from this cross will have apricot eyes ?
a. all
b. ¾
c. ½
d. ¼
e. none

2. What fraction of the female progeny from this cross will have apricot eyes ?
a. All
b. ¾
c. ½
d. ¼
e. none

3. What fraction of the total progeny from this cross will have pale orange eyes ?
a. all
b. ¾
c. ½
d. ¼
e. none

4. The interaction between the while ( w ) and apricot ( wa ) alleles is an example of
a. reduced penetrance
b. pleiotropy
c. incomplete dominance
d. complete dominance
e. codominance

It is a little know fact that Gregor Mendel was inspired to do his now famous experiments with pear plants because of some genetic crosses made by his older brother , Melvin Mendel. Unfortunately , Melvin was neither as bright nor as careful as his brother.

Melvin experimented with the plant okra

In one of his crosses, Melvin crossed pure breeding plants with red okra to pure breeding plants with blue okra. He inbred the F1 progeny to produce an F2.

In the F2 he recovered the following

Plants with red okra 28
Plants with blue okra 72

1. Melvin forgot to record the phenotype of the F1 plants which most likely was:
a. all red
b. all blue
c. all purple
d. all red and blue
e. ½ red , ½ blue

2. Melvin crossed the F1 plants to some pure breeding blue plants but he spilled his coffee on the paper with the results. Most likely what he was
a. all of the progeny were blue
b. all of the progeny were red
c. ½ of the progeny were red, ½ were blue
d. ¾ of the progeny were red ¼ were blue
e. ¼ of the progeny were red ¾ were blue

3. The type of cross that Melvin made in the previous question is called
a. a test cross
b. a back cross
c. an inbreeding cross
d. a self cross
e. a test cross

Melvin also did some blood typing of himself his brother Gregor and their parents. Melvin found out that he had type AB blood and that Gregor had type O blood. Unfortunately his god ate the shet of paper with his parents blood type. Most likely his parents blood type would have been

a. one type O and one type AB
b. one type A and one type AB
c. one type B and one type AB
d. one type A and one type B
e. both type AB

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Solution Summary

The genetics are analyzed by using punnet squares. A heterozygous males and females are analyzed for a single gene locus with two alleles.

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