1. A recessive, mutant allele, black, causes dark body color in Drosophila. Wild-type color is gray. Give the genotypic and phenotypic ratios of the offspring from a crossing between a black female and a gray male, whose father was black. If you had a gray female, what would you do to determine her genotype?
2. Retinoblastoma is an eye cancer caused by a dominant allele. A normal female and an affected male have four children: One normal and three affected. What is the father’s genotype? What are the genotypes of all of the offspring?
3. If purple flower color is dominant to white
in sweet peas, determine the genotypes of the parents in the following crosses:
Purple x Purple = 22 Purple and 7 White b)
Purple x White = All purple
c) Purple x White = 16 Purple and 14 White
4. Phenylketonuria (PKU) is inherited as a recessive disorder in humans. Two unaffected parents have three children, one with PKU. What is the probability the fourth child will have PKU?
5. In the garden pea, Mendel found that Yellow seed color (Y) was dominant to Green (y) and Round seed shape (R) was dominant to wrinkled (r). a) In the P generation we have a homozygous Yellow, Round (both dominant) x homozygous green wrinkled (both recessive). What is the F2 Phenotypic ratio? b) What is the phenotypic ratio of Yellow : Green and Smooth : Wrinkled? c) What Mendelian principle is responsible for these results?
6. In a dihybrid cross, four hundred offspring were produced and the offspring were equally divided into four different phenotypic classes. What were the most probable genotypes of the parents? Would you arrive at the same conclusion if there were only four offspring?
7. In chili peppers, Long (L) is dominant over short (l), and Hot (H) is dominant over mild (h). a) What is the phenotype of a pepper with the genotype of Llhh? b) What gametes can be produced from Llhh? c) What is the phenotype of a pepper with llHh?
8. In dogs, Floppy ears (F) are dominant over Erect ears (f) and Black fur (B) is dominant over White fur (b). A diheterozygote is crossed with a dog homozygous recessive for ear shape and heterozygous for fur color.
a) What is the genotype of the diheterozygote?
b) What is the genotype of the dog heterozygous for fur color and homozygous recessive for ear shape?
c) What is the phenotypic ratio of the offspring in the cross described?
9. In daisies, yellow petals (Y) are dominant
over white petals (y) and Black centers (B) are dominant over orange centers
(b). Two plants with Yellow petals and
Black centers are crossed and the following offspring were produced:
45 Plants with Yellow petals and Black centers 14
Plants with Yellow petals and Orange centers 16 Plants with White petals and Black
centers 5 Plants with White petals
and Orange centers