Reference no: EM133307414
1. This question will enable you to show what you learned about monohybrid crosses.
Saguaro cacti are very tall, cylindrical plants that usually have two L-shaped arms, one on each side. Suppose you lived in southern Arizona where the Saguaro cactus is common, and you happen to have one growing in your yard. Your Saguaro has two arms, but one is longer than the other. Now, assume that arm length in these cacti are controlled by a single gene with arms of the same length (A) being dominant to arms of different lengths.
a. What is the genotype of your cactus?
b. Could one of the parents of your cactus have a phenotype with arms of the same length? If so, what would have been the genotype of the parent cactus?
c. Using the method you learned, please use a Punnet square to write out the genetic cross the supports your answer to part b.
d. Suppose you cross your cactus with that of your neighbor, which has arms of the same length. Your great-grandchildren (it takes a Saguaro cactus a long time to mature) find that half of the resulting offspring have arms the same length and half have arms of different lengths. What was genotype of your neighbor's cactus?
e. Using the method you learned, please use a Punnet square to write out the genetic cross the supports your answer to part d.
2. This question will enable you to demonstrate what you learned about dihybrid crosses.
About 70% of Americans perceive a bitter taste from the chemical phenyltiocarbamide (PTC). The ability to taste this chemical results from a dominant allele (T) and not being able to taste PTC is the result of having two recessive alleles (t). Albinism is also a single locus trait with normal pigment being dominant (A) and the lack of pigment being recessive (a). A normally pigmented woman who cannot taste PTC has a father who is an albino taster. She marries a homozygous, normally pigmented man who is a taster but who has a mother that does not taste PTC.
a. Indicate the genotypes of the normally pigmented woman and the normally pigmented man in this problem.
b. Using what you learned about conducting Punnet squares, please write out the dihybrid cross between these two individuals.
c. What are the phenotypes of the possible children?
d. What percentage of the children will be albinos?
3. We discussed how a test cross can help identify the genotype of pea plant with green peas, which could be caused by a GG phenotype or a gg phenotype.
a. What is a test cross?
b. Why can't test crossed be performed in humans? Please address both scientific and ethical drawbacks.