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Punnett Squares

Punnett Squares. OGT. 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. What is a trait?.

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Punnett Squares

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  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

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