Biology: Principles of genetics

Please complete this homework assignment and upload it to Canvas by Monday April 27th (11:59pm). This assignment accounts for 50 points. Please answer the questions in this Word document.

Name:

In foxes, two alleles of a single gene (P and p) may result in lethality (PP), platinum coat (Pp), or silver coat (pp).

1. What phenotypic and genotypic ratios are observed in young pups when platinum foxes are bred? (5 pts)

2. Is the P allele behaving dominantly or recessively in causing lethality? Explain your answer. (4 pts)

The type of plumage found in mallard ducks is determined by three alleles at a single locus: MR, which encodes restricted plumage; M, which encodes mallard plumage; and md, which encodes dusky plumage. The restricted phenotype is dominant over mallard and dusky; mallard is dominant over dusky (MR > M > md).

3. Give the expected phenotypic proportions of offspring produced by the cross below. Show the Punnett square calculations for a full credit. (8 pts)

MRmd × MRM

The pedigree below shows the inheritance of the ABO blood groups in a human family:

4. What is the genotype of “1”? (3 pts)

5. Individual “9” got its A allele from his: (2 pts)

a) Mother

b) Father

c) Could be either

6. What are the possible genotypes of “4”? (3pts)

Consider the following biosynthetic pathway: Gene A encodes an enzyme that converts a yellow pigment to an orange pigment. Gene B encodes an enzyme that converts the orange pigment to a red pigment. Assume the two genes are unlinked (they assort independently). Assume a and b are recessive loss-of-function alleles for genes A and B, respectively.

7. What is the genotype of a true-breeding (homozygous) red individual? (2 pts)

8. What is the genotype of a true-breeding orange individual? (2 pts)

9. What are the possible genotypes of a true-breeding yellow individual? (2 pts)

10. What is the phenotype of an AaBb individual? (2 pts)

While you have extra time on your hands (right? 😉) and you are quarantined at home during the COVID-19 pandemic, you decided to pursue a hobby interest of yours – growing African violets. You decided to cross a true breeding blue plant with a true breeding pink one. All the F1 offspring were blue.

Still with lots of free time, you decided to cross the F1 blue plants with each other and the resulting F2 generation was a mix of blue and pink flowering plants. Much to your surprise there was also a 3rd phenotype, red flowering!

You carefully counted the F2 plants and realized they nicely fit this ratio:

9/16 blue

3/16 red

4/16 pink

11. Based on this information and your new genetics knowledge from this class, what are the genotypes for the F2 generation that give rise to the phenotypic ratios you are seeing? Provide the genotypes for each generation, including parents. (9 pts)

In some goats, the presence of horns is produced by an autosomal gene that is dominant in males, while is recessive in females.

12. A hornless male is crossed with a horned female. The F1 offspring are intercrossed to produce the F2. What proportion of the F2 females will have horns? (5 pts)

13. Why is the horned trait not considered a sex-limited trait? (3 pts)