Patterns of Heredity

1. How is this trait passed on? Patterns of Heredity In how many species is Albinism seen? Lecture 1 Dias ECFHS How common is this?

2. I. History Lycopersicon to tomato • For most of history, mechanism for inheritance was unknown. 1. Hippocrates (400 BC)– “Particles from the body travelled to sperm and eggs.” 2. Blending Theory: parent traits mix. Like “yellow and blue paint” make green. • Doesn’t explain how blue eyes could re-emerge later. B. Selective Breeding – Breeding plants or animals with good traits to emphasize them in offspring. • Most modern crops and animal breeds are the result of selective mating by humans. Teosinte to corn

3. C. Case Studies • Is it possible to domesticate wild foxes? • How many generations would it take? • Is Alcoholism hereditary? • Is it linked to impulsive behavior? 3.How similar are identical twins separated at birth?

4. II. Gregor Mendel • The father of modern heredity. 1. Kept records of 29,000 pea plants breedings. • Published theory of heredity in 1866. • Work rediscovered 40 years later. Wanted to know: • What was physically passed from parents to offspring? • Could traits be mathematically studied and predicted?

5. B. Compared 7 different traits with 2 forms each. 1.-Purple vs. white flower, etc. 2. Peas are Self-Pollenating • Pollen fertilizes an egg within the same flower. 3. Used True-breeding plants • Had the same sets of traits every generation.

6. C. Mendel forced cross-pollination • Brushed pollen from purple plant onto egg of white flower 1. Grew the peas into plants. D. Results • P generation (parents) • Purple Flower x White Flower • F1 Generation – Offspring of P gen. All were PURPLE. • Purple was dominant. White was recessive. • What should Mendel do next? P Gen. F1 Gen.

7. G. Mendel’s explantion: • Each organism has 2 copies, or alleles of • the color gene. Dominant allele is capital letter “R”. • P Gen. were Homozygous: matching alleles. • Genotype: “RR”. • Phenotype: Purple • White allele is “r”. White plant’ genotype was “rr”. • 3. One parent gave “R”, other gave “r”, so all F1 were Rr. - Heterozygous: having one of each allele. ”Hybrids” • Allowed F1 plants to self-pollinate. • Seeds grew into the F2 generation (“grandkids”): • Of 929 plants, 705 were purple, 224 white. • 75% purple to 25% white - 3:1 ratio F2 gen

8. Steps for solving: Rr x Rr • Genotypes • RR, Rr, rr. • 1:2:1 ratio • Phenotyperatio: • - 3 purple: 1 white V. Punnett Square

9. Case studies - Silver Fox • Starting in 1959, selective breeding of the most friendly ones. Domesticated in 40 generations. • rounded ears, curly tails show up in 9 generations.

10. Case Studies revealed… • Two groups of mice bred for 30 gen.: produced high-volume alcohol drinkers, and others that avoided it. • A gene codes for an enzyme that breaks down nicotine in the liver. Highly active and slower forms. • People with the more active gene get rid of nicotine faster, so they need their next cigarette sooner. Harder to quit.

11. The “Jim” twins Met for the first time at 39 years old. Both 6’ tall, 180 lbs, each had a childhood dog named Toy, married a woman named Linda, divorced, then married a “Betty”, named their sons James Alan and James Allan, were part-time sheriffs, enjoyed carpentry, had severe headaches, smoked Salems, and drank Miller Lite beer.

12. Heredity 2 - More MendeI • Law of Segregation – Each sperm or egg carries one chromosome from each homologous pair. Body Cell B b Gamete b B

13. Law of Independent assortment A. Of the 23 pairs of chromosomes in humans, one from each pair is selected randomly. • How many possible combination in eggs? • (2)23

14. III. Dihybrid Cross Mendel bred plants varying in two traits – • Crossed true-breeding round (R), yellow seed (Y) plant, with green (y), wrinkled plant (r). • P Gen: RRYY x rryy • F1 Gen : RY RY RY RY ry RrYy • All offspring are RrYy ry ry ry

15. B. He then self-pollinated the F1 • RrYy x RrYy • Each parent’s gametes: RY, Ry, rY, or ry • What’s the phenotype ratio?

16. Practice Problem In flies, the wild-type phenotypes for eye color and wing shape are red eyes(R) and normal wings (N). White eyes are recessive, and so are small, useless wings, which are termed “vestigial”. • Cross a male, heterozygous for both traits, with a white eyed, vestigial-wing female. • RrNn x r r n n

17. Answer rN r n RN Rn • red normal, red vestigial, white normal, and white vestigial. • Ratio- 1:1:1:1 r n

18. Heredity 3 - Beyond Mendel A. Incomplete Dominance • No recessive allele. A heterozygote has an intermediate phenotype. • Flowers: R-red allele, W – white • RW is pink. B. Codominance • A heterozygote shows full expression of both alleles. • Flowers: RW is white with red spots or patches.

19. C. Most lethal diseases are recessive. Why? • Dominant disorders can’t “hide”. • Huntington’s Disease - Dominant. • mental deterioration beginning at age 40ish. • Adult onset allows victim to reproduce before the disease appears.

20. MULTIPLE ALLELES -more than 2 • 3 alleles for blood type: A, B, and O a. “O” allele doesn’t code for a marker on RBC’s. • “A” = specific marker • B = “B” marker. (BB or BO gives type B blood) • Codominance: Getting “A” from one parent and “B” from the other leads type AB.

21. E. Why Blood Type Matters • Antibodies - immune proteins that attack a specific antigen (foreign protein). • People with Type A blood have “anti-B” antibodies that will attack Type B RBCs received in a transfusion. • Type A person can receive? _______ • Type B can receive?_____ Type AB person?______________ • Type O person? ______ This is the “universal donor” • Who is the universal recipient? ____________ A, O O, B A, B, AB, O O AB Antigen Antibody in blood that attacks a specific antigen

22. F. Polygenic Traits 1. Most traits are affected by multiple genes. • Example: Skin color genes.

23. IV. Sex Linked Traits A. Case Study: The Royal Bloodline • In the 1800’s, Royal families in Europe intermarried to strengthen alliances. • Russia: Czar Nikolas II married Alix, granddaughter of Victoria, Queen of England. • Had 4 daughters, then son Alexis, heir to the throne. • Alexis had hemophilia, which prevents blood clotting. A bruise or small cut can cause death.

24. Sex Linked Traits

25. Sex-Linked Traits • Women have 2 X-chromosomes, men have XY. 1. Y is smaller, lacking many genes found on X. - Doesn’t provide a back-up copy of a defective allele on X. • Result: Color Blindness, hemophilia, baldness are more common in men. • 1. If “N” is gene for normal eyesight, and “n” for red-green colorblind-ness. • Written as XN or Xn. • b. Carrier woman • XNXn. • A color blind man • XnY

26. Little Miss Sunshine Scene

27. B. Sex-Linked Problem PROBLEM: An unaffected man marries a carrier woman. Probability a son would have hemophilia? Daughter? • Hemophilia allele: • Xh • Normal allele: • XH • Genotypes of parents: • XHY x XHXh • Perform Punnett Sq. • Son w/ hemophilia: • ½, or 50% • Daughter • 0% • 50% will be carriers

28. C. Heredity Practice Problems • On Jerry Springer, a couple want to settle whether their child was fathered by the man, or the plumber. • Blood Types: Man - B, Woman AB, Plumber - O, Child - A. • Who is the baby-daddy? • Can’t tell by blood type. Woman gave “A” gene, either man could have given an “O”. • The plumber goes back on Jerry Springer later. He is only 21 and starting to go bald (a sex-linked trait). He wants to publicly blame his father, who is also bald, and maybe fight him on TV. • Is it plumber-daddy’s fault? Explain • NO. Daddy is bald due to a gene on his X chromosome. But he gave his son a Y. • Who should you look at to see if you may go bald?

29. V. Pedigree A. Tracks certain trait through generations of a family. • By tracking phenotypes, genotypes can be deduced. • Males – squares Females - Circles • Affected with disease/ trait: Shaded • Unaffected: unshaded • Parents - connected with a horizontal line • Offspring - below parents, with line connecting. B

30. Queen Victoria’s daughters had 50% chance of getting her Xh. These carriers gave hemophilia to half their sons. • The Royal family focused on curing Alexis as Russian society crumbled and WWI raged. They were killed in the 1918 Bolshevik revolution. B. Case Study- Hemophelia