1. Genetics: Part I Mendel and the Gene

2. 2 Marfans Syndrome Cleft chin Colorblindness Polydactyly Widows peak Freckles

3. Mendelian Genetics What do you remember about Mendel and his genetics studies from your first biology course? What are some of the terms of genetics that you remember? 3

4. Can you define these? Genotype Phenotype Monohybrid Dominant Recessive P 1 Homozygous Heterozygous Allele Test cross F 1 F 2 4

6. Phenotype Purple White 3 1 1 1 2 Ratio 3:1 Ratio 1:2:1 Genotype PP (homozygous) Pp (heterozygous) pp (homozygous)

9. Figure 14.1

10. P p

11. 3. The pattern of inheritance (monohybrid, dihybrid, sex-linked, and genes linked on the same homologous chromosome) can often be predicted from data that gives the parent genotype/ phenotype and/or the offspring phenotypes/genotypes. Curriculum Framework

12. Mendelian Genetics Law of Dominance - if the two alleles at a locus differ, then one (the dominant allele) determines the organism’s appearance, and the other (the recessive allele) has no noticeable effect on appearance 12

13. Human Traits with simple dominance : Widows peak Handedness Free earlobes Cleft Chin Dimples Freckles PTC testing Polydactyly Bent little finger Nearsightedness Mid-digit hair 13

14. Frequency of Dominant Alleles Dominant alleles are not necessarily more common in populations than recessive alleles For example, one baby out of 400 in the United States is born with extra fingers or toes Dominant does not mean numerous

15. In humans, alleles for dark hair are genetically dominant, while alleles for light hair are recessive. Which of the following statements is/are most likely to be correct? a.Dark hair alleles are more common than light hair alleles in all areas of Europe. b.Dark hair alleles are more common than light hair alleles in southern Europe but not in northern Europe. c.Dark hair alleles are equally common in all parts of Europe. d.Dark hair is dominant to light hair in southern Europe but recessive to light hair in northern Europe.

16. b. Segregation and independent assortment of chromosomes result in genetic variation. 1. Segregation and independent assortment can be applied to genes that are on different chromosomes. 2. Genes that are adjacent and close to each other on the same chromosome tend to move as a unit; the probability that they will segregate as a unit is a function of the distance between them. Curriculum Framework

17. Mendelian Genetics Law of segregation: the two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes 17

18. Figure 14.7 Dominant phenotype, unknown genotype: PP or Pp ? Recessive phenotype, known genotype: pp Predictions If purple-flowered parent is PP If purple-flowered parent is Pp or Sperm Eggs or All offspring purple 1 / 2 offspring purple and 1 / 2 offspring white Pp pp p ppp P P P p TECHNIQUE RESULTS

19. Figure 14.8 P Generation F 1 Generation Predictions Gametes EXPERIMENT RESULTS YYRR yyrr yr YR YyRr Hypothesis of dependent assortment Hypothesis of independent assortment Predicted offspring of F 2 generation Sperm or Eggs Phenotypic ratio 3:1 Phenotypic ratio 9:3:3:1 Phenotypic ratio approximately 9:3:3:1 315 108 101 32 1/21/2 1/21/2 1/21/2 1/21/2 1/41/4 1/41/4 1/41/4 1/41/4 1/41/4 1/41/4 1/41/4 1/41/4 9 / 16 3 / 16 1 / 16 YR yr 1/41/4 3/43/4 Yr yR YYRR YyRr yyrr YYRRYYRrYyRR YyRr YYRrYYrr YyRr Yyrr YyRR YyRr yyRR yyRr YyRr YyrryyRr yyrr

20. Independent Assortment 20

21. Practice In order to solidify your ability to explain the Laws of Segregation and Independent Assortment, describe how these laws would apply as sperm cells are developed in a man with genotype RrSs. Draw an image to support your explanation. 21

22. Sample image 22

23. Imagine crossing a pea heterozygous at the loci for flower color (white versus purple) and seed color (yellow versus green) with a second pea homozygous for flower color (white) and seed color (yellow). What types of gametes will the first pea produce? a. two gamete types: white/white and purple/purple b. two gamete types: white/yellow and purple/green c. four gamete types: white/yellow, white/green, purple/yellow, purple/green d. four gamete types: white/purple, yellow/green,white/white, and purple/purple