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The Punnett Square

The Punnett Square. How is this possible??:. Where do offspring inherit traits from?. Offspring inherit genes for particular traits from their parents. Genes for a particular trait normally come in pairs. Cont. Each parent normally has two alleles for a single trait.

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The Punnett Square

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  1. The Punnett Square

  2. How is this possible??:

  3. Where do offspring inherit traits from? • Offspring inherit genes for particular traits from their parents. • Genes for a particular trait normally come in pairs

  4. Cont. • Each parent normally has two alleles for a single trait. • We use a Punnett square to determine the possibilities of the combinations of alleles that the offspring may receive.

  5. What is a Punnett Square? • A Punnett square is a tool used to predict the ratio or percentage of the possible genes that an offspring will have based on the genes of the parent.

  6. Mendel Video Clip

  7. In a Punnett square, the top of the table shows the alleles provided by one parent. • The alleles for the other parent are placed along the left side of the table. How do you set up a Punnett Square

  8. How do you use a punnett square? • One allele from each parent is placed in the individual squares, forming a new gene pair. • The individual squares show the possibilities of allele pairs in the offspring.

  9. For example, the following table shows the cross Tt x tt:

  10. In this example, tallness (T) is the dominant trait and shortness (t) is the recessive trait. • As the Punnett square shows, TT, Tt, and tt are all possible genotypes for the height of the offspring.

  11. The offspring with the genotypes TT and Tt will have a phenotype of tall. • The offspring with the genotype of tt will have a phenotype of short.

  12. If the two alleles are the same (TT or tt), the genotype is purebred or homozygous • If the two alleles are different (Tt), the genotype is hybrid or heterozygous.

  13. Monohybrid cross - a cross that shows the inheritance of a single characteristic. Pea Shape

  14. It is sometimes difficult to predict certain traits because there may be several different genes that control these traits • example: eye color and hair color

  15. A a A a Try This A a A A

  16. a a A a a a a a

  17. A A A A a a A A

  18. Question!! B = Brown b = White How did the tiger pups turn out white instead of brown?

  19. How is this possible??: B = Brown Eyes b = Blue Eyes

  20. Practice Quiz!! • http://www.quia.com/quiz/220564.html

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