1. Chapter 14 – Mendel and the Gene Idea

2. Gregor Mendel Mid 19 th century Austrian monk

3. Garden pea Self fertilize or cross fertilize True breeding or hybrids

4. Garden pea traits

5. Experimental design – monohybrid cross

6. Terminology “factors” = genes –Alleles Dominant Recessive

7. Terminology cont Phenotype Genotype –Homozygous –Heterozygous

8. Interpretation of monohybrid cross Law of Segregation

9. Testcross To determine genotype of dominant individual

10. Experimental design – dihybrid cross Law of independent assortment

11. Extensions of Mendelian inheritance All of Mendel’s traits were coded for by a single gene and had only two alleles – with one being completely dominant over the other Not all traits are that simple

12. Incomplete dominance Heterozygote has an intermediate phenotype

13. Epistasis One gene masks the effects of another gene

14. Environmental effects Phenotype is affected by environmental influence of gene expression

15. Multiple alleles & Codominance Some genes have more than two alleles present in a population Codominance – heterozygote expresses both alleles

16. Blood type cont Rh factor –Mendelian inheritance “+” completely dominant over “-” –Erythroblastosis fetalis

17. Polygenic inheritance Continous traits

18. Pleiotropy One gene having multiple effects

19. Pedigree analysis

20. Recessive – albinism Dominant – Achondroplasia

21. Prenatal testing