1. Patterns of Inheritance

2. Ancestry and Obesity In The News

3. Historical Views of Inheritance Hippocrates (~ 400 B.C.) –Particles given off from bodies of father and mother –Offspring was mixture Homunculus (pre-1900) –Each sperm contained a tiny preformed human

4. Gregor Mendel Austrian Monk Worked with garden peas Discovered process of heredity

5. Suitability for Using Peas Each flower has male & female parts Sex organs are enclosed & protected Pollination can be controlled

6. True-breeding Generations of self-fertilization produce consistent offspring Mendel used true-breeding varieties

7. Mendel’s Experiments Artificially crossed true-breeding plants Recorded offspring from cross-fertilization

8. Characters Used by Mendel 7 true-breeding traits Monohybrid crosses

10. Mendel’s Crosses Example: –Tall plant crossed with short plant –Hybrid offspring (F 1 ) were not intermediate –Resembled only one parent

11. F 1 of Hybrid Cross Dominant – form expressed in F 1 Recessive – form not expressed in F 1

12. Mendel’s Next Step Allowed F 1 to self fertilize F 2 expressed dominant & recessive forms Ratio in F 2 = 3:1 (dominant:recessive)

13. Mendel’s Monohybrid Crosses

14. Conclusions of Mendel’s Work Traits are inherited as genes Alleles are alternate forms of genes Gametes receive only 1 allele of each pair Alleles may differ or may be identical

15. Mendel’s Law of Segregation Each gamete receives only one of an organisms pair of alleles, and which one it receives is determined by chance

16. Alleles of an Individual Homozygous – identical alleles for a trait Heterozygous – different alleles for a trait

17. Genotype An organisms allelic makeup Dominant designated by capital letter Recessive designated by small letter

18. Phenotype Expression of alleles Dominant gene is expressed if present

20. Punnet Square Diagram to predict possible combinations

21. Test Cross Determining Genotype

22. Dihybrid Crosses Are Traits Linked?

23. Law of Independent Assortment The transmission of alleles for one trait into gametes does not affect the transmission of alleles for other traits

26. Location of Mendel’s Factors Mendel did not know where traits were located Chromosomes were discovered 22 years after Mendel’s work was published Walter Sutton suggested that Mendel’s factors were on chromosomes

27. Thomas Hunt Morgan Studied fruit flies, Drosophila melanogaster Discovered different traits in flies Experiments to test Mendelian inheritance

28. Morgan’s Cross White-eyed male Red-eyed female (normal eye color) Eye color followed Mendel’s 3:1 ratio However, all white-eyed F 2 were males

30. Conclusion of Morgan’s Experiment White eyes were linked to males Trait was found on X chromosome Females have two X chromosomes

31. Conclusion of Morgan’s Experiment Traits are located on chromosomes Some traits are sex-linked

32. End chapter 13