Download Dominant-Recessive Inheritance Problems

Dominant-Recessive Inheritance Problems
Directions: Complete the following questions. Please show your work with Punnett Squares where necessary.
1. Define: a) gene, b) chromosome, and c) genetics.
2. How many chromosomes are in the: a) human body cells such as skin and muscle and b) human reproductive
cells such as sperm and ova?
3. What are the sex chromosomes of a human male, and of a human female?
4. What is meant by the term “pure-bred”?
5. Distinguish between a genotype and a phenotype.
6. If two organisms have the same phenotype, does this mean they have the same genotype?
7. In peas, yellow color is dominant to green. What will be the colors of the offspring of a cross between: a) a
homozygous yellow and a green pea plant, b) a heterozygous yellow and green pea plant, c) a heterozygous yellow
and a homozygous yellow pea plant, and d) two plants that are hybrid for the yellow pea seed?
8. Could two brown-eyed parents have a blue-eyed child? Explain.
9. Could two blue-eyed parents have a brown-eyed child? Explain.
10. A blue-eyed man, both of whose parents were brown-eyed, marries a brown-eyed woman whose father was
blue-eyed and whose mother was brown-eyed. This man and this woman have a blue-eyed child. What are the
genotypes of all the individuals mentioned?
11. If two animals heterozygous for a single pair of genes mate and have 200 offspring, about how many have the
dominant phenotype?
Monohybrid Cross:
12. Let’s say that in seals, the gene for the length of the whiskers has two alleles. The dominant allele (W) codes for
long whiskers and the recessive allele (w) codes for short whiskers.
a. What percentage of offspring would be expected to have short whiskers from the cross of two longwhiskered seals, one that is homozygous dominant and one that is heterozygous?
b. If one parent seal is pure long-whiskered and the other is short-whiskered, what percentage of
offspring would have short whiskers?
Dihybrid Cross:
13. In watermelons, a solid green (G) color is dominant over the striped pattern (g), and the short, round shape (S)
is dominant over long shape (s). What will be the phenotypic ratio of a cross between a homozygous green and
heterozygous short watermelon with a heterozygous green and long watermelon?
Trihybrid Cross:
R = round
r = wrinkled
T = tall
t = short
Y = yellow
y = green
14. Cross a pea plant heterozygous for shape, homozygous recessive for height, and homozygous dominant for
color with a pea plant homozygous recessive for shape, homozygous dominant for height, and heterozygous for
color.