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Punnett Squares and Genetics

1) Assume the gene for dimples, d, is recessive. Then assume that two individuals with the genotypes Dd and dd mate. Create a Punnett square for this mating and state the probability that their offspring will have dimples.

2) Briefly explain epistasis.

3) List the steps of mitosis and briefly describe what happens in each.

4) What is the role of mRNA in the synthesis of proteins?

5) What is an intron?

6) In the process of protein synthesis, what is the difference between transcription and translation?

7) For animals, what is the advantage of internal fertilization and what type of species utilize it?

8) What is the reproductive purpose of fruits?

9) What is the genetic advantage of sexual reproduction?

Assignment Expectations:

Provide a short but thorough answer to each question. In doing so, you will demonstrate your understanding of the principles of inheritance, the molecular basis of genetics, and the structure of reproduction.

Solution Preview

1) Assume the gene for dimples, d, is recessive. Then assume that two individuals with the genotypes Dd and dd mate. Create a Punnett square for this mating and state the probability that their offspring will have dimples.
Response:

D d
d Dd dd
d Dd dd

After the Punnett square showing that Dd X dd, the resulting offsprings have 50% Dd and 50% dd indicating that 50% of the population will have the recessive alleles for dimples. So the probability that the offspring will have dimples is 50%.

2) Briefly explain epistasis.

Response:

The scientific definition of epistasis is a "situation in which the differential phenotypic expression of genotypes at one locus depends upon the genotype at another locus. " (1)
Similar, an "epistatic gene allele of one gene eliminates expression of the alternative phenotypes of another gene, and inserts its own phenotype instead. " (1)
For example, let look at color inheritance in dogs.

Two alleles of gene B and b determines black and brown furs, respectively.

B = Black fur
B= brown fur

A separate gene E encode for color deposition in the coat, and ee genotype prevents color deposition in the coat resulting in golden phenotype.
Thus, dogs with genotype BBEE have black coat fur, dogs with bbEE have brown coat with color deposition. Dogs with BBee or bbee have golden coat because the ee genotype prevents color deposition. Thus, the ee is a recessive epistasis.

3) List the steps of mitosis and briefly ...

Solution Summary

The expert creates a Punnett square for the mating. The probability of their offspring will have dimples is determined.

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