1. Mendelian Genetics – inheritance of traits

2. Why Peas?? Many varieties (character, traits) Easy to control pollination Could choose distinct characters

3. First Experiments: True-breeding parent generation Why aren’t all the floweres light purple?

4. Mendel’s Law of Segregation White “heritable factor” did not disappear in F1 generation but only purple “heritable factor” was acting.  Alternative version of genes (heritable factors) account for variations in inherited characters.  For each character, an organism inherits two alleles (versions of the gene) one from each parent.  If the two alleles differ, one is fully expressed – DOMINANT; the other does not affect the organism’s appearance - RECESSIVE trait.  The two alleles segregate during gamete production

5. Mendelian Genetics Terms Homozygous Heterozygous Phenotype Genotype Punnett square Monohybrid cross Testcross

7. What happens if looking at two traits simultaneously? Dihybrid cross x True-breeding Parent (P) F1 F2: 9:3:3:1

9. Mendel’s Law of Independent Assortment Each character is independently inherited – segregate independently during gamete formation Practice dihybrid crosses Use rules of probability to predict outcomes of genetic crosses

10. http://www.biology.arizona.edu/me ndelian_genetics/problem_sets/mo nohybrid_cross/monohybrid_cross.h tml

11. More Complicated Situations… 1.Incomplete dominance

12. Multiple Alleles I A I A = A; I A i = AI B I B =B; I B i = B I A I B = ABii = O A, B – codominant i - recessive

13. Other situations: Pleiotropy – one gene affects several phenotypes Epistasis – one gene affects the phenotypic expression of another gene Polygenetic inheritance – additive effect of two or more genes on a single phenotypic character

15. Human Disorders that follow Mendelian Patterns of Inhertitance Recessively inherited disorders: albinism, cystic fibrosis, Tay-Sachs disease, sickle-cell anemia Dominantly inherited disorders: Achondroplasia, Huntington’s disease

16. Cystic Fibrosis

17. Tay-Sachs Disease

18. Achondroplasia

19. Huntington Disease Late Acting – middle age Western Europeans

21. Screening for inherited disorders

22. Pedigrees

23. Pedigree – Huntington disease

24. Pedigree – Sickle cell anemia

25. Chromosomal Theory of Inheritance Thomas Morgan Fruitflies 4 pairs of chromosomes Wild type phenotype Mutant phenotype White-eyed males only

26. Sex-linked traits Located on Sex chromosomes: X or Y Females XX; Males XY X-linked recessive Hemophilia, color blindness