1. Notes – Punnett Squares

2. Vocabulary Terms Phenotype = physical appearance of a trait
Example: purple flowers
Genotype = the combination of alleles that an individual has for a particular gene
Example: PP or Pp or pp

3. Vocabulary Terms Homozygous = having two of the same alleles
Example: PP or pp
Heterozygous = having two different alleles
Example: Pp

4. Punnett squares predict the offspring genotypes
Use these steps:
Determine the genotypes of parents
Determine the alleles in the gametes
Combine gametes: bring over and down
Analyze the results
Phenotype ratio
Genotype ratio Pp P p PP Pp pp
3 purple : 1 white
1PP : 2Pp : 1pp

5. Oral Practice: What are the phenotypes of the parents?
What are the genotypes of the parents?
What are the genotypes and phenotypes of the offspring in the top row?
What are the genotypes and phenotypes of the offspring in the bottom row?
Pair-share: one student answers the odds and the other answers the evens.

6. Practice #1
In peas, the gene for tall (T) is dominant to the gene for short (t). Predict the offspring genotype and phenotype ratios if a plant that is heterozygous tall is crossed with a plant that is short? Reminder: Follow the steps in your notes to create a Punnett square.