Baby steps through Punnett squares, then some practice problems:

Phenotypes or genotypes? Aa TT gG

Phenotype or genotype? Blue eyes Pink flowers Yellow peas

Aa What is the recessive allele?

Aa What is the dominant allele?

AA What is the genotype AA? a. Homozygous recessive b. Heterozygous c. Homozygous dominant

Aa What is the genotype Aa? a. Homozygous recessive b. Heterozygous c. Homozygous dominant

aa What is the genotype aa? a. Homozygous recessive b. Heterozygous c. Homozygous dominant

Aa x aa What is the genotype of parent 1?

A= afro, dominant, a=no afro What will Aa phenotype be, afro or no afro?

A= afro, dominant, a=no afro What will aa phenotype be, afro or no afro?

A= afro, dominant, a=no afro What will AA phenotype be, afro or no afro?

A person is heterozygous for Afro. What is their genotype? Aa aa AA

A person is homozygous dominant for Afro. What is their genotype? Aa aa AA

A person is homozygous recessive for Afro. What is their genotype? Aa aa AA

1. Aa x aa Parent Genotypes:________________ Genotypic Ratio: _______________ Phenotypic Ratio: _______________

2. Tt x Tt Parent Genotypes:________________ Genotypic Ratio: _______________ Phenotypic Ratio: _______________

Cross two plants that are heterozygous for green pods Cross two plants that are heterozygous for green pods. [Note: green (G) is dominant over yellow (g)] Parent Genotypes:________________ Genotypic Ratio: _______________ Phenotypic Ratio: _______________

Cross a homozygous tall plant with a short plant Cross a homozygous tall plant with a short plant. [Note: tall (T) is dominant over short(t)] Parent Genotypes:________________ Genotypic Ratio: _______________ Phenotypic Ratio: _______________

5. In purple people eaters, one-horn is dominant (H) and no horns is recessive (h). Draw a Punnett Square showing the cross of a purple people eater that is heterozygous for horns with a purple people eater that does not have horns. Summarize the genotypes & phenotypes of the possible offspring. Parent Genotypes:________________ Genotypic Ratio: _______________ Phenotypic Ratio: _______________

6. Mendel found that crossing wrinkle-seeded plants (r) with pure round-seeded plants (R) produced only round-seeded plants.  What genotypic & phenotypic ratios can be expected from a cross of a wrinkle seeded plant & a plant heterozygous for this trait? Parent Genotypes:________________ Genotypic Ratio: _______________ Phenotypic Ratio: _______________

7. In humans, brown eyes (B) are dominant over blue (b) 7. In humans, brown eyes (B) are dominant over blue (b). A brown-eyed man marries a blue-eyed woman and they have three children, two of whom are brown-eyed and one of whom is blue-eyed. Draw the Punnett square that illustrates this marriage. SHOW YOUR WORK! What is the man’s genotype? Explain. What is the woman’s genotype? Explain. What are the genotypes of the children?

Case #1 (If he is DD) Case #2 (If he is Dd) 8. In dogs, there is a hereditary deafness caused by a recessive gene, “d.” A kennel owner has a male dog that she wants to use for breeding purposes if possible. The dog can hear, so the owner knows his genotype is either DD or Dd. If the dog’s genotype is Dd, the owner does not wish to use him for breeding so that the deafness gene will not be passed on. This can be tested by breeding the dog to a deaf female (dd). Draw the Punnett squares to illustrate these two possible crosses. Case #1 (If he is DD) Case #2 (If he is Dd)   In each case, what percentage/fraction of the offspring would be expected to be hearing in each case? In each case, what percentage/fraction of the offspring would be expected to be deaf? How can you tell the genotype of this male dog?