Genetics Homework

Q1. In a cross with homozygous dominant and homozygous recessive parents (P-generation), what proportion of the offspring in the F-2 generation (if you self-cross the F-1 Generation) would exhibit the phenotypic characteristic of the recessive parent?

Q2. In a test cross, the individual with the unknown genotype is crossed with an individual with what genotype?  

Q3. In human blood types, which blood type best represents codominance?

Q4. Which human blood type allele is recessive to two different alleles?

Q5. In snapdragons the two alleles for flower color belong to one gene and this gene exhibits incomplete dominance. What will be the phenotypes of a cross of a red snapdragon with a white snapdragon?

Q6. Albinism is an autosomal recessive trait. A normally pigmented man marries an albino woman. If their first child was an albino what would their (the parents) genotypes and their child's genotype be? If they have more children what other genotypes could there be?

Q7. An albino man marries normally pigmented woman. They have 13 children all of whom are normally pigmented. What are the probable genotypes of the children and parents?

Q8. A normally pigmented marries an albino woman. The man's father was an albino. The woman's parents were both normally pigmented. The man and woman have three children, two normally pigmented and one albino. List each of these persons and give their probable genotypes.

In Drosophila, the fruit fly, wild type long wings "G" is dominant over vestigial wing (g).

Q9. In a cross between heterozygous long-winged male and a vestigial-winged female, what types and proportions of genotypes would be expected?

Q10. In a cross between two heterozygous long-winged flies, what types and proportions of genotypes would be expected?

Q11. If a heterozygous long-winged fly mated with a homozygous long-winged one, what percentage of the offspring would be expected to be homozygous long-winged? Would there be any vestigial-winged flies?

Q12. A long-winged fly mated with a vestigial-winged fly producing 35 long-winged and 35 vestigial-winged offspring. What are the genotypes of the parents? Of the long-winged offspring? Of the vestigial-winged offspring?

Q13. Mating a long-winged fly with a vestigal-winged fly produced 256 offspring all of which were long-winged. What were the probable genotypes of the parents? Mating of the F1 long-winged flies together would produce what types of offspring genotypically and in what proportions?

Q14. In human beings, a downward-pointed frontal hairline ("widow's peak") is a heritable trait. A person with widow's peak always has at least one parent who also has this trait, whereas persons with a straight frontal hairline may occur in families in which one or even both parents have widow's peaks. When both parents have a straight frontal hairline, all children also have a straight hairline. Using A and a to symbolize alleles for this trait, what is the genotype of an individual without widow's peak? (Show your reasoning).

Q15. The first of three children of two normally pigmented parents has albinism, a recessive trait that results from lack of the pigment melanin.

a. Given that the normal allele is A and the albino allele is a, draw this pedigree and label both the phenotypes and genotypes.

b. What is the probability that the second child, who shows normal pigmentation, is a carrier?

c. What is the probability that both unaffected children are carriers? INCLUDE LOGIC STATEMENT(s).

d. What is the probability that only one of the two unaffected children is a carrier? INCLUDE LOGIC STATEMENT(s).