1. Punnett Squares OGT

2. What are Punnett squares ? • They are tables that allow us to predict the traits of offspring • They are a visual, hypothetical cross between parents • Punnett squares are named for an English geneticist, Reginald Punnett

3. What is a trait? • Every expressed trait is the result of the interaction of two genes (alleles) • Each parent contributes one allele to this interaction • Pair of genes (alleles) is known as genotype • They will determine what is seen

4. Certain traits are seen whenever that allele is present • These are dominant traits • Other traits will only be seen when both alleles are present • These are recessive traits

5. Letters are used to represent alleles • Uppercase (capital) letters are used for dominant alleles • Lowercase (small) letters are used for recessive alleles

6. Pea pod color can be green or yellow • The dominant color is green • The recessive color is yellow • “G” will represent the green allele • “g” will represent the yellow allele

7. Practice 1 • Rabbit fur can be grey or white • Dominant color is grey • Recessive color white • Dominant allele ? • Recessive allele ?

8. If both alleles of a pair are the same • The alleles are called homozygous alleles • These genotypes are homozygous Notice they can be upper or lower case GG BB TT gg bb tt

9. These alleles are homozygous dominant GG BB TT • These alleles are homozygous recessive gg bb tt

10. If both alleles of a pair are different • The alleles are called heterozygous alleles • These genotypes are heterozygous Gg Bb Tt

11. Completing a Punnett • Figure out the dominant & recessive traits • Give the traits letters • Sketch the cross GG x Gg ♂ ♀

12. 4. Separate and position the alleles G g

13. 5. Perform the cross G g

14. Look at the results • 2 have the GG genotype - 50% • 2 have the Gg genotype - 50%

15. End Punnett Squares