1) Red-Green color blindness is an X-Linked recessive trait in humans, whereas p
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Question
1) Red-Green color blindness is an X-Linked recessive trait in humans, whereas polydactyly is an autosomal dominant trait. Consider a female that has normal color vision and is not polydactyl, whose mother has the same phenotype but whose father is polydactylous and red-green colorblind. If this person has offspring with a male who is both polydactyl and color-blind, what are the expected phenotypes of the offspring?
2) In Drosophila, yellow eyes, Y, are dominant to grey eyes, y. In an experiment, Dr. D breeds two individuals, one with yellow eyes and the other with grey. He finds the offspring to be 131 yellow and 58 grey.
What are the genotypes of the adult that were crossed?
What is the expected proportion of individuals in each group and do these numbers significantly differ?
Are there other possible genotypes for the adults? Is there statistical support for them?
3) In corn, crossing two pure breeding lineages produced the following offspring: 2625 green seedlings, 656 yellow seedlings, and 219 white seedlings.
What are the genotypes for the seedlings?
Explain how the phenotype is produced.
Is this epistatic? If so identify the hypostatic locus.
4) Maternal genetic effects are complicated. The coiling of the shell for the snail Limnaea peregra is controlled by an autosomal locus. Right turning (dextral), s+, is dominant over left turning s (sinistral).
If an animal is sinistral, can it be s+s+?
Can a sinistral animal have siblings that are dextral?
Will all the offspring of a sinistral individual also be sinistral?
Explanation / Answer
1)
Based on your data, here the mother as normal color vision and is not polydactyl, but she may act as carrier. Thus, the cross between a carrier and an affected person results 1/2 of the males with color blindness and 1/2 the of the females act as carriers. Thus, the expected phenotypes of this cross are: 50% affected and 50% carriers.
2) Here, the Y is dominant to y
The genotypes of the adult that were crossed are: Yy (yellow) and yy (grey)
The other possible genotypes for the adults are: YY (yellow)
3)
The genotypes of three seedlings are: GG green seedlings, Gg yellow seedlings, and gg white seedlings.
In the F2 population always the dominant phenotype prevails, thus green is a complete dominant phenotype. The least phenotype that is expressed in F2 generation is a complete recessive phenotype: white. And the yellow phenotype is expressed in F1 and F2 it is due to union of gametes from green and white.
Yes, it is an intermediate epistasis, the hypostatic locus is: g.
4)
s+s+ is the homozygous dominant genotype for dextral, so a sinistral animal cannot be s+s+. A sinistral animal only has one possible genotype, and that's ss.
A sinistral animal can have siblings who are dextral if its parents are both heterozygous, because one child can adopt the s allele from each parent, while the other can adopt an s+ allele from one or both parents.
The offspring of a sinistral individual can be sinistral of the other parent is either heterozygous or also sinistral (i.e. homozygous recessive).
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