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Dominant/Recessive:
1. What is the difference between a pure breed and a hybrid breed?
2. What is the difference between genotype and phenotype?
3. If both parents have brown eyes and their two children have blue eyes, what can you say
about the genotypes of the parents?
4. Draw a Punnett square for a cross between a tall pea (Tt) and a short pea (tt). What will
the offspring look like?
5. Plants of a certain species have either red or white flowers, where red (R) dominates
white (r).
a. If pure red-flowered plants are crossed with hybrid red-flowered plants, what
percentage of the offspring will be plants with red flowers?
b. If pure red-flowered plants are crossed with pure white-flowered plants, what
percentage of the offspring will have red flowers? What percentage will have white
flowers?
c. If two hybrid red-flowered plants are crossed, what will be the ratio of offspring with
red flowers to offspring with white flowers?
6. A brown animal is crossed with a white one. All the offspring are brown. What does this
suggest about the gene for brown colour?
7. Albinism is a hereditary condition in which skin pigments are not formed. Normal skin
pigmentation (P) is dominant over albinism (p).
a. What are the possible genotypes for a person with normal skin pigmentation?
b. What are the possible genotypes for a person with albinism?
c. If the first child of a married couple with normal phenotypes is an albino, what are the
chances that their second child will also be an albino? Explain your answer.
8. The gene for a long nose (N) is dominant over the gene for a short nose (n).
a. What possible genotypes can a long-nosed person have?
b. What possible genotypes can a short-nosed person have?
c. If a pure long-nosed person marries a person who has a short nose, what types of
noses can their children have? Show reasons.
9. In Mendel’s pea experiment, pure yellow-seeds were crossed with pure green-seeds. Why
were all the first generation plants yellow-seeds? Why were ¾ yellow and ¼ green in the
second generation?
10. Brown eyes (B) dominates blue eyes (b). If one parent has pure brown eyes and the other
parent has pure blue eyes, then the possible genotypes for their offspring are
________________. The possible phenotypes are ___________________.