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Genetic Questions

1. In Burmese cats, brown coat color is dominant to tan coat. Brown coat is a highly prized trait in Burmese. You have a brown male cat that you would like to offer as a stud; therefore, you need to know if it is homozygous or heterozygous for brown coat color.
A. Why is this important?
B.Diagram a testcross that would determine the genotype of your cat, and what the outcome would be if your cat were a homozygote or a heterozygote(genotype and phenotype).

2. Purple eyes is a dominant autosomal mutation found on chromosome 3 of drosophila. Eyeless is a recessive atosomal mutation found on chromosome 2. A true-breeding purple-eyed male is crossed with a true-breeding eyeless female (assume that she has no purple alleles, but instead has the normal red-eyed alleles):
A.What are the genotypes of the P1 flies (use correct genetic symbols)?
B.What would be the genotype and phenotype of the F1 progeny?
C.If a F1 female is mated to a red-eyed male whose mother was eyeless, use the forkline method to determine the expected phenotypic ratio of their progeny? The expected genotypic ratio of their progeny?

3. In humans, assume that brown eyes(B) are dominant to blue (b); and right-handedness (R) to left-handedness(r). A right-handed, blue-eyed man marries a right-handed, brown-eyed woman. They have 2 children, one left-handed and brown-eyed and the other right-handed and blue-eyed. By a later marriage with another woman who is also right-handed and brown-eyed , this man has nine children, all of whom are right-handed and brown-eyed. What are the genotypes of this man and his 2 wives?

4. Each letter combination shown below indicates the genotype of a diploid organism. Up to three different loci, each with 2 possible alleles (A or a;B or b; C or c) are under consideration. For each of these individuals, indicate the genotypes and gametic ratio of ALL possible gametes that can be produced. (hint:remember that gametes are haploid!)
A. AABb
B.AaBbCc
C.aaBBCc

5. Discuss whether the following individuals are: 1)gonadally male or female,2)phenotypically male or female (discuss Wolffian/Mullerian ducts and external genitalia),and 3)sterile or fertile:
A.XY, homozygous for a recessive mutation in the cytosolic receptor for testosterone, which renders the gene nonfunctional.
B.XX, heterozygous for a dominant mutation in the MIH gene, which causes continuous production of MIH.
C.XY, with a mutation which renders the SRY gene nonfunctional.

6. What sex would each of the following karyotypes produce?Humans normally have 46 chromosomes and Drosophila melanogaster has 8 in a normal diploid cell.
Find XO, XXX, XXY In humans and In drosophila....

Solution Preview

Please find the attached solution.

1.In Burmese cats, brown coat color is dominant to tan coat. Brown coat is a highly prized trait in Burmese. You have a brown male cat that you would like to offer as a stud; therefore, you need to know if it is homozygous or heterozygous for brown coat color.

A. Why is this important?

Solution:

• We can find out the gametic nature of male brown cat
• We can find out whether that is sex linked inherited or not
• By which we can find out that whether that is true breeding or not

B. Diagram a testcross that would determine the genotype of your cat, and what the outcome would be if your cat were a homozygote or a heterozygote(genotype and phenotype).

Let us assume that

Brown coat color---------BB
Tan coat color-----------bb

Brown coat color is dominant to tan coat colour, so even in the presence of single allele (B) brown color can express.

Test cross:

If the cat is in homozygotic condition (brown color)

BB X bb (test cross with homozygotic recessive gamete)

Bb Bb Bb Bb (progeny)

Result shows that all are brown color and indicating 100% of result, which means gametic nature of all offspring are same. So the Brown color of that crossed cat (parent) is in homozygous condition.

If the cat is in heterozygotic condition (brown color)

Then the cross will be

Bb X bb (test cross)

Bb Bb bb bb (progeny)
The result shows that 50% are in brown color and 50% are in tan color. So it shows that the parent gametic (crossed) nature is heterozygous one.

2. Purple eyes is a dominant autosomal mutation found on chromosome 3 of drosophila. Eyeless is a recessive atosomal mutation found on chromosome 2. A true-breeding purple-eyed male is crossed with a true-breeding eyeless female (assume that she has no purple alleles, but instead has the normal red-eyed alleles):

A. What are the genotypes of the P1 flies (use correct genetic symbols)?
B.What would be the genotype and phenotype of the F1 progeny?
C.If a F1 female is mated to a red-eyed male whose mother was eyeless, use the forkline method to determine the expected phenotypic ratio of their progeny? The expected genotypic ratio of their progeny?

Solution:

Purple eyes is a dominant autosomal mutation one -----------CP
Eyeless is a recessive atosomal mutation-------------------------pp

A true-breeding purple-eyed male is crossed with a true-breeding eyeless female

CP X pp (parent)

Cp Cp Pp Pp (offspring)----F1 progeny

All the progeny has red colored eyes. So to express purple color C and P, both alleles are need. Eventhough offspring ...

Solution Summary

The solution assists with answering the given genetic questions.

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