1. Mendel and Heredity (Chapter 8) D. Blanck PLHS Biology D. Blanck PLHS Biology

2. I. Orgins of Genetics: A.Heredity: the passing of traits from parents to offspring (Characteristic=Trait)  before DNA and chromosomes were discovered, heredity was a great mystery A.Heredity: the passing of traits from parents to offspring (Characteristic=Trait)  before DNA and chromosomes were discovered, heredity was a great mystery

3. B. Gregor Johann Mendel: 1) Austrian monk that is credited as the “ father ” of the scientific study of heredity 2) Experimented with different varieties of garden peas a) 1 st to develop rules to predict patterns of heredity B. Gregor Johann Mendel: 1) Austrian monk that is credited as the “ father ” of the scientific study of heredity 2) Experimented with different varieties of garden peas a) 1 st to develop rules to predict patterns of heredity

4. b) heredity provides the basis for: Genetics – the study of “ genes ” c) repeated experiments of T.A. Knight  Mendel extended Knight ’ s work by applying math! (ratios and proportions) b) heredity provides the basis for: Genetics – the study of “ genes ” c) repeated experiments of T.A. Knight  Mendel extended Knight ’ s work by applying math! (ratios and proportions)

5. 3. Why did Mendel use garden peas? a) Peas have clear traits - easy to tell apart (see table 8-1, pg 163) b) Easy to control pollination (male and female parts are in same flower) 1) self-fertilization – flower fertilizes itself 2) cross-pollination – transfer of pollen between plants c) Easy to grow 3. Why did Mendel use garden peas? a) Peas have clear traits - easy to tell apart (see table 8-1, pg 163) b) Easy to control pollination (male and female parts are in same flower) 1) self-fertilization – flower fertilizes itself 2) cross-pollination – transfer of pollen between plants c) Easy to grow

6. C) Mendel’s work with ratios: 1. Mendel ’ s Experiment monohybrid cross – only 1 trait Step 1: Make sure plant is true-breeding  allow plant line to self-pollinate for many generations  results in no variation in traits C) Mendel’s work with ratios: 1. Mendel ’ s Experiment monohybrid cross – only 1 trait Step 1: Make sure plant is true-breeding  allow plant line to self-pollinate for many generations  results in no variation in traits

7. Step 2: Cross two “ P ” generation (parental generations) plants with contrasting traits  observe offspring (F 1 generation)  record # of F 1 plants with each trait Step 2: Cross two “ P ” generation (parental generations) plants with contrasting traits  observe offspring (F 1 generation)  record # of F 1 plants with each trait

8. Step 3: Allow F 1 plants to self-pollinate  observe and count this second generation of offspring = F 2 generation Step 3: Allow F 1 plants to self-pollinate  observe and count this second generation of offspring = F 2 generation

9. 2. Mendel ’ s results: a) F 1 gen. – showed only one form of trait (ex: purple flowers) b) F 2 gen. – showed both forms of trait (ex: 705 purple: 224 white) c) For each of the 7 traits, he found the same 3:1 ratio! 2. Mendel ’ s results: a) F 1 gen. – showed only one form of trait (ex: purple flowers) b) F 2 gen. – showed both forms of trait (ex: 705 purple: 224 white) c) For each of the 7 traits, he found the same 3:1 ratio!

10. Mendel’s results for other traits

11. results2

12. II. Gene Theory: A. Mendel ’ s Hypothesis - “ foundation of genetics ” 1. For each trait, an individual has 2 copies of the gene, one from each parent 2. There are alternative versions of genes II. Gene Theory: A. Mendel ’ s Hypothesis - “ foundation of genetics ” 1. For each trait, an individual has 2 copies of the gene, one from each parent 2. There are alternative versions of genes

13. Alleles = alternative forms of a gene (green seed vs yellow seed)  1 allele for each gene comes from each parent Genotype = set of 2 alleles ex: GG or gg (G = green and g= yellow) Phenotype = observable characteristic ex: pea appears green or yellow Alleles = alternative forms of a gene (green seed vs yellow seed)  1 allele for each gene comes from each parent Genotype = set of 2 alleles ex: GG or gg (G = green and g= yellow) Phenotype = observable characteristic ex: pea appears green or yellow

14. Homozygous = 2 identical alleles for a trait (ex: GG and gg) Heterozygous = 2 different alleles for a trait (ex: Gg or gG) Homozygous = 2 identical alleles for a trait (ex: GG and gg) Heterozygous = 2 different alleles for a trait (ex: Gg or gG)

15. 3. When 2 different alleles occur together, one may be completely expressed. The other may have no observable effect on phenotype a) Dominant = allele exclusively expressed: PP = purple Pp = purple b) Recessive = allele NOT expressed when dominant form is present: Pp = Purplepp = white 3. When 2 different alleles occur together, one may be completely expressed. The other may have no observable effect on phenotype a) Dominant = allele exclusively expressed: PP = purple Pp = purple b) Recessive = allele NOT expressed when dominant form is present: Pp = Purplepp = white

16. III. Studying Heredity: A. Punnett Square – predicts the expected genotypes of a cross.

17. Punnett squares can also deal with multiple or complex traits. A = Green a = absence of Green (blue) B = Brown b = absence of Brown (blue) Punnett squares can also deal with multiple or complex traits. A = Green a = absence of Green (blue) B = Brown b = absence of Brown (blue)

18. Color Blindness An X-Linked Trait

19. Codominance or incomplete dominance