Heredity and Genetics

1. Heredity and Genetics Study of the Inheritance of Traits Chapter 10-11 Textbook

2. Objectives • Explain Mendel’s laws of segregation and independent assortment, and their role in inheritance • Demonstrate results of sexual reproduction with dominant/recessive traits, incomplete dominance, codominance, and sex-linked traits like hemophilia and color-blindness.

3. Objectives • Prepare a position about intentional gene modification, mutation. • Defend and support your position in either a powerpoint or a paper. • Analyze bioethics and science in public policy and law.

4. What are Genes? • Genes control the looks of mice, flies, people, and all other living things.

5. Chromosomes • Contain Genes • Genes are codes for proteins, which give us our body traits • Genes, found on chromosomes, have 1 to 8 alleles per trait • An Allele is 1 copy of a gene on each of the two chromatids of a chromosome allele Gene

6. Genes and alleles ...

7. How Were Genes Discovered?

8. Gregor Mendel (1822-1884) • Mendel was the gardener in a Monastery in Brno, Czech Republic in 1850’s • Discovered principles of genetics by experimenting with 900 pea plant crosses

9. Mendel’s experiment • Mendel cut off pollen producers (anthers) of flower to prevent self-pollination of peas • He then pollinated this plant with a plant having a different trait. • He tallied the results of the crosses.

10. Mendel’s experiment… • He cross-pollinated pea plants of different characteristics • Height of plant • Pea pod color • Pea pod texture • Flower position

11. Mendel’s first principle Segregation

12. P Generation (parent) • Mendel crossed a Tall pea plant with a short pea plant • Mix of two breeds is called a hybrid

13. F1 Generation (1st offspring) • Mendel found that the offspring were all Tall plants • Trait for Tallness showed up in all 1st generation offspring • The short trait disappeared.

14. Terms… • The trait that shows up is called Dominant • The trait masked or hidden by the dominant allele is called recessive

15. Phenotype • Traits or looks are called phenotype • The phenotype could be tall, short, etc.

16. The genotype • We represent genotype by two letters • One represents the mother’s gene • The other represents the father’s gene. • TT genotype plant would be tall phenotype • tt genotype plant would be short phenotype • Tt genotype plant would be tall phenotype

17. Terms • TT is called homozygous dominant genotype • Homozygous recessive genotype: tt • Tt is called heterozygous dominant genotype

18. Mendel then crossed the Hybrid Tall F1 plants • 3/4 offspring were Tall and 1/4 offspring were short. • The recessive trait had reappeared in the 2nd generation

19. Segregation • In a hybrid cross, the recessive trait disappears in the F1 generation then reappears in F2 generation. • If you cross a purebred Tall plant with a purebred short plant, the 1st generation will all be Tall. • If you cross the 1st generation plants their offspring will be ¾ Tall and ¼ short.

20. 1st Conclusion of Mendel male pollen • Genes control traits from parent to offspring • Offspring inherit one set of genes from each parent. • Organisms have two sets of alleles per gene for each trait. female ovule New seed

21. 2nd principle of Mendel • How are traits passed to offspring?

22. Independent Assortment • The two chromsomes carrying the genes/alleles are Independently separated during anaphase of meiosis • The genes for different traits (hair color, eye color, etc) may be passed to offspring independently of the other traits.

23. Mendel’s Conclusions • Offspring inherit one gene from each parent. • Genes control traits from parent to offspring. • Two or more genes can produce a trait in a person • One gene could be Dominant and mask the other recessive gene making the offspring show the dominant trait • Both genes could be dominant and the offspring could have the dominant trait • Both genes could be recessive and the offspring will have the recessive trait.

24. Punnett Square

25. Building a Two Trait Punnett Square • Tt • Bb • Assemble a 4 square punnet square to see which alleles will pair for each parent.

26. Two trait (Dihybrid cross) • Take the allele combinations for each parent and place them on the side of a 16 square Punnet Square

27. Two trait (Dihybrid cross) • There will be four letters in each box • Usually we put the Capital or Dominant first • Offspring will have a 9:3:3:1 ratio

28. Video on Mendel’s laws and Punnet Squares • https://www.youtube.com/watch?v=Mehz7tCxjSE • Mendel • https://www.youtube.com/watch?v=Y1PCwxUDTl8&spfreload=10 • Punnet

29. Incomplete Dominance • Two alleles are neither dominant nor recessive • A red rose crossed with a white rose can produce a pink rose. Neither white nor red is dominant so they both mix.

30. Codominance • Both alleles are dominant • A red horse or cow and a white horse or cow produce a roan horse or cow with red and white hairs

31. Codominance • A white chicken and a black chicken crossed can produce a black & white striped chicken • Both white and black show up

32. Punnett Square with Codominance • Each allele is dominant so each offspring will inherit the trait from the father and mother. Both show up in offspring

33. Codominance in Horses and Cows • Red and White produce a Roan. Both traits are produced in offspring

34. Codominance in chickens and flowers

35. Sex-linked Traits • Males have an X chromosome and a y chromosome (Xy) • All pairs match up but one pair • Females have two X chromosomes (XX) • All pairs match up • Traits can be masked in females by another dominant allele • Traits in males on the X chromosome are alone. The y chromosome carries different information.

36. Color blindness

37. Sex-linked traits • Eye color in Fruit Flies

38. Hemophilia (blood clotting problems) • Video: • Queen Victoria’s son

39. Further information • http://www.sonic.net/~nbs/projects/anthro201/exper/ • http://www.blc.arizona.edu/courses/181gh/rick/genetics1/mendel.html