Mendel ’ s Principle of Dominance or Recessiveness

1. Mendel’s Principle of Dominance or Recessiveness Traits found in humans Modified by Mrs. Snyder January 2015

2. What is the relationship between DNA and your physical appearance? • Take a moment to think about what you know about DNA, chromosomes, and ribosomes. Write down several ideas. • Now, look at the image to the right. • What are genes? See page 111

3. What are genes?

4. If genes control traits, then we need to find out how they do this. • Two alleles exist for each gene (because chromosomes are paired.) (page 111) • For now we will keep things simple. • The presence or absence of an allele impacts an organism’s appearance. • The terms dominant, recessive, homozygous, and heterozygous are important for you to understand.

5. Terms defined • Dominant – page 109 • Recessive – page 109 • Homozygous vs heterozygous • How are alleles represented? • Probability: pages 111- 113

6. Explore 1 • Fundamentally Genetics • You and your groups will be looking at each other to determine whether you are dominant or recessive for the following traits.

7. More terms • Genotype • phenotype

8. Tongue Rolling

9. Earlobes

10. Earbump • Often called Darwin’s Ear Bump • Dominant - Having a small bump on the ear • Recessive - Not having the bump

11. Widow’s Peak

12. Hitchhiker’s Thumb

13. Cleft Chin

14. Clockwise Hair Whorl

15. Here is the link to the lab we are going to do • Obtain a lap top when directed. • Create an excel chart • It should have 8 columns • Label as directed

16. Period 3 Lab: Partners – randomly generated • John, Rebecca • Laura, Ilana • Tae, Jessie • Alex, Gino • Kylie, Maria • Grace, Justin • Andrew, Robert • Nia, Gianna • DJ, Cooper You are a team of scientists. You are studying the random distribution of traits (this occurs during meiosis) and will use your traits as an example. One person is the “mother” and one is the father.

17. Period 7 Partners – randomly generated You are a team of scientists. You are studying the random distribution of traits (this occurs during meiosis) and will use your traits as an example. One person is the “mother” and one is the father.

18. Period 8 Partners – randomly generated You are a team of scientists. You are studying the random distribution of traits (this occurs during meiosis) and will use your traits as an example. One person is the “mother” and one is the father.

19. Explore 2 • Punnett Squares • You will be able to predict the outcomes of crosses by completing this next activity.

20. Explain • Mendel & The Gene Idea

21. Mendel and Genetics • Answer the following questions as we explain the concepts surrounding basic genetic

22. It All Began with Mendel (FYI) • Gregor Mendel was born in 1822. • Called the “Father of Genetics” • Late 1800 chromosomes and the process of meiosis were unknown. • Mendel’s work was considered obscure and unimportant until 1900 • Walter Sutton proposed the Chromosome Theory and people began to listen to his ideas. • Chromosome Theory – specific genes are located on specific chromosomes

23. Three Conclusions to His Research • Principle of Dominance and Recessiveness One allele in a pair may mask the effect of the other • Principle of Segregation The two alleles for a characteristic separate during the formation of eggs and sperm • Principle of Independent Assortment The alleles for different characteristics are distributed to reproductive cells independently.

24. Mendelian genetics • Character (heritable feature, i.e., fur color) • Trait (variant for a character, i.e., brown) • True-bred (all offspring of same variety) • Hybridization (crossing of 2 different true-breds) • P generation (parents) • F1 generation (first filial generation)

25. Genetic vocabulary……. • Punnett square: • Gene: point on a chromosome that controls the trait • Allele: an alternate form of a gene A or a • Homozygous: identical alleles for a character • Heterozygous: different alleles for a gene • Phenotype: physical traits • Genotype: genetic makeup • Testcross: breeding of a recessive homozygote X dominate phenotype (but unknown genotype)

26. How can the Chances of an Offspring’s Traits be Determined? • BY USING A PUNNETT SQUARE • Get out your Punnett Squares Problems • In groups of two come to the board and complete the given monohybrid problems.

27. Bb X BbPhenotypic Ratio3:1Genotypic Ratio1:2:1 B b B B B B b b B b b b

28. Exploration 4 • What about two traits? • Complete the second half of your Punnett Square Problems

29. What about 2 Traits? • BbTt x BbTt • The Gametes contain one of each of the alleles. (BT). • Each of the offspring contain four alleles exactly like the parents.(BbTt). • Notice the number of possible offspring has increased. • The phenotypic ratio is 9:3:3:1

30. BbTt x BbTt

31. Exceptions to Mendel’s Rule

32. Incomplete Dominance • The phenotype of the heterozygote is intermediate between those of the two homozygotes. • Ex) Snap Dragon Color • Red, Pink, White

33. Co-dominance • Phenotype of both homozygotes are produced in heterozygotes individuals. • Both alleles are expressed equally. • Ex)Roan Cattle White-feathered birds are both homozygotes for both B and W alleles

34. Multiple Alleles • Ex )Blood type • Blood type A and B are co-dominant, while O is recessive. • Forms possible blood types of A, B, AB, and O.

35. Blood Also Shows Codominance

36. Sex-Determination • Chromosome pairs 1-22 are autosomes • Chromosome pair 23 are sex chromosomes • They determine the sex of an individual • XX = female XY = male

37. Sex-Linked Inheritance • Traits that are only found on the X chromosome • Colorblindness and Hemophilia are examples of sex-linked traits. • These genes are recessive and found only on the X chromosome.

38. Polygenic Inheritance • Inheritance pattern of a trait that is controlled by two or more genes. • Gene may be on the same chromosome or on different chromosomes. • Ex) Skin color and Height

39. ELABORATION 1Exceptions to the Rule Punnet Squares: Dihybrid, Sex-Linked, Multiple Alleles, Co-Dominance, Incomplete Dominance

40. Elaboration 2 • Who’s the Parents? • Upon completion of this lab, you will: • determine the ABO blood types of two sets of parents and two newborn children • examine the genetic relationships possible between the parents and children • match the “mixed up” children with their proper parents.