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Mendelian Inheritance & Principles

Mendelian Inheritance & Principles. (Chapter 2- Brooker Text). November 20, 2007 BIO 184 Dr. Tom Peavy. Theory of Pangenesis Theory of Preformationism Blending Theory of Inheritance. Central Question. How are traits inherited?. Theory of preformationism ( homunculus).

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Mendelian Inheritance & Principles

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  1. Mendelian Inheritance & Principles (Chapter 2- Brooker Text) November 20, 2007 BIO 184 Dr. Tom Peavy

  2. Theory of Pangenesis Theory of Preformationism Blending Theory of Inheritance Central Question How are traits inherited?

  3. Theory of preformationism (homunculus)

  4. Skip Ahead to the 21st Century: • We know the genetic information (DNA) is organized within • Chromosomes • We receive one homologous chromosome from each parent • ♂n + ♀n = 2n (new unique individual) Human Genome Project http://www.ncbi.nlm.nih.gov/

  5. DATA FROM MENDEL’S MONOHYBRID CROSSES

  6. Mendel’s Law of Segregation During gamete formation, the paired factors segregate randomly so that half of the gametes received one factor and half of the gametes received the other

  7. Dihybrid Crosses Crossing individual plants that differ in two traits • For example • Trait 1 = Seed texture (round vs. wrinkled) • Trait 2 = Seed color (yellow vs. green) • There are two possible patterns of inheritance for these traits

  8. DATA FROM DIHYBRID CROSSES

  9. Interpreting the Data • The F2 generation contains seeds with novel combinations (ie: not found in the parentals) • Round and Green • Wrinkled and Yellow • These are called nonparentals • Their occurrence contradicts the linkage model

  10. DATA FROM DIHYBRID CROSSES

  11. Law of Independent assortment • During gamete formation, the segregation of any pair of hereditary determinants is independent of the segregation of other pairs

  12. Problem Solving

  13. Dihybrid Cross TtYy x TtYy

  14. Problem Solving TtYy x ttyy What is the expected phenotypic ratio among offspring?

  15. Tt RR x Tt RR What fraction of the progeny will be Tall and Round?

  16. (pg 38)

  17. Alternative = Forked Line Method

  18. Alternative = Forked Line Method

  19. Alternative = Forked Line Method

  20. Tt RR Yy x Tt RR Yy What fraction of the progeny will be Tall, Round, and Green?

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