1. Punnett Square Notes
Biology - Ms. Spinale

2. Gene - particular piece of genetic information on a chromosome.
Terms to Know
Chromosome - DNA molecules organized around structural proteins; contains enough information for many phenotypic traits.
Gene - particular piece of genetic information on a chromosome.

3. Terms to Know

4. Allele - different versions of the same gene.
Terms to Know
Allele - different versions of the same gene.
Example: blood type, eye color.
In sexual reproduction, individuals have 2 alleles for each gene - 1 from each parent.

5. Homozygous - 2 identical alleles of a gene.
Terms to Know
Homozygous - 2 identical alleles of a gene.
Example: in blood types, AA or BB.
Heterozygous - 2 different alleles of a gene.
Example: in blood types, AB.

6. Terms to Know
Dominant trait - trait that presents itself whether the individual is homozygous or heterozygous; represented by a capital letter.

7. Terms to Know
Recessive trait - trait that presents itself only in homozygous individuals; masked by the dominant trait in heterozygous individuals; represented by a lowercase letter.

8. Genotype - genetic information in an organism.
Terms to Know
Genotype - genetic information in an organism.
Phenotype - observable traits (physical characteristics).

9. Monohybrid cross - looks at 1 trait.
Punnett Squares
Punnett squares are used to predict the outcome of a cross between genotypes of two individuals.
Monohybrid cross - looks at 1 trait.
Dihybrid cross - looks at 2 traits.
Trihybrid cross - looks at 3 traits.

10. Punnett Squares
This is an example of a monohybrid cross between 2 heterozygous individuals.

11. Punnett Squares

12. Steps for Solving Punnett Square Problems
1. Define what traits are dominant and recessive (pick a letter to represent if necessary)
2. Determine who the parents are and their genotypes.

13. Steps for Solving Punnett Square Problems
3. Fill in the Punnett Square.
4. Calculate genotype and phenotype probabilities.

14. Practice Problem
Red roses are dominant over white roses. Use a Punnett Square to predict the phenotypic and genotypic outcomes of a cross between a heterozygous red rose and a white rose.

15. Practice Problem
1. Define what traits are dominant and recessive (pick a letter to represent if necessary)
Dominant: _____
Recessive: _____
Possible genotypes: __________________

16. 2. Determine who the parents are and their genotypes.
Practice Problem
2. Determine who the parents are and their genotypes.
Parent 1: _______________
Parent 2: _______________

17. 3. Fill in the Punnett Square.
Practice Problem
3. Fill in the Punnett Square.
4. Calculate genotype and phenotype probabilities.