Mendelian Genetics

1. Mendelian Genetics Chapter 10 and 12

2. Gregor Mendel (a little history) • “Father of Genetics” • Conducted experiments on heredity with pea plants.

3. Mendel’s Work With Pea Plants • Garden Peas

4. Mendel’s Work With Peas

5. Example cross: What do you think the offspring will look like?

6. The Results (F1 generation)

7. The Results (F2 generation)

8. Generations • Notice that Mendel looked at 3 generations in his crosses. • Generations: • P = the original Parents (the first ones he crossed • F1= the offspring of the P generation • F2 = the offspring of the F1 generation

9. Important Vocabulary • Heredity—the passing on of characteristics from parents to offspring • Genetics—study of heredity • Traits– inherited characteristics • Gametes • Fertilization • Zygote

10. Do you recall… • Answer the following: • Gregor _______ is the Father of ______. • Heredity is the passing of ______. • Genetics is the study of ________.

11. More Vocabulary: • Gene= section of DNA on a chromosome that controls a specific trait. • Allele: alternate form of a gene • Ex. tall allele vs. short allele for the “height gene”

12. Vocab… • Dominant—the trait that is observed (masks the other allele) in a hybrid. • Upper case letter • Recessive—the trait that gets masked (not observed) in a hybrid • Lower case letter

13. Is the trait dominant or recessive? This is a ______ trait. T

14. Is the trait dominant or recessive? This is a ______ trait. e

15. Vocab… • Phenotype Vs. Genotype • Genotype—The gene combination of the organism (i.e. BB, Bb or bb.) • Phenotype – the way an organism looks and behaves as a result of its genotype (i.e brown)

16. Vocab… • Homozygous vs. heterozygous • Homozygous—has two of the SAME alleles for a trait • Ex. • Heterozygous—has two DIFFERENT alleles for a trait Ex. • Carrier = a carrier is heterozygous. • In a heterozygous creature, which trait will show up as the organism’s phenotype?

17. Genetics Vocab Assignment

18. How to Solve Genetics problems • READ and Make a Key • ex. B= black fur, b= white fur • Parent genotypes (Write them down) • ex. BB x Bb • Gametes (Figure out what the gametes would be & put them on Punnett square) • Fill in Punnett square to get offspring • Phenotypes/Genotypes of offspring (Write them out)– Best if written as a reduced fraction! • Example…

19. Cross for one characteristic Example: Hair color B b B BB Bb B BB Bb Monohybrid Cross Punnett Square C:\Documents and Settings\BBAUGHMAN\Desktop\bio powerpoints\Chapter 10 BDOL IC

20. Practice Problems • 1. In pea plants, tall (T) is dominant to dwarf (t). Show the cross between a heterozygous tall and a dwarf plant. • a. What are the expected genotypes and phenotypes and in what proportion? • b. Show the cross between two heterozygous tall plants. What are the expected genotypes and phenotypes and in what proportion?

21. In goats, a recessive gene causes the goats to "faint" when they are startled. A farmer breeds two goats (that have never fainted) and their first offspring faints two days after its birth. What must the parent's genotypes have been? Show the cross to prove it. • http://www.youtube.com/watch?v=we9_CdNPuJg FAINTING GOATS VIDEO CLIP

22. Dihybrid Cross • Cross with two characteristics at the same time • Example: • Seed Color AND • Seed shape 2 types of genes

23. DIHYBRID crosses (how to perform them) • Exm. Parents = RrYy x RrYy • Make a key • Write out parents. • Use FOIL method to determine gametes • FOIL = first, outer, inner, last • Write out possible gametes. • Place the father’s gametes on the side and the mother’s on the top. • Use a 16 square Punnett square (4x4)

24. Practice Problems • In guinea pigs, short hair is dominant to long hair. Also in guinea pigs, black eyes are dominant to red eyes. A male guinea pig that is heterozygous for both traits is crossed with a female that is long haired and red eyed. • a. What are the expected phenotypes of their offspring and in what proportion? • b. If both parents are heterozygous for both traits, what are the expected phenotypes of their offspring and in what proportion?

25. Mendel’s Laws • Law of Segregation • When gametes are made, allele pairs segregate (separate). • Then alleles randomly recombine at fertilization (with the alleles of the other parent).

26. Law of Independent Assortment • Genes for different traits (ex. Height and seed color) are inherited independently of each other. • (i.e. how tall you are will NOT affect what color your seeds are)

27. Genetics Problems Review • On a separate piece of paper, make up three genetics problems as follows: • 1. an easy monohybrid problem • 2. a difficult monohybrid problem • 3. a dihybrid cross • You can make up any traits you like. Feel free to be creative. ex. Unibrows are dominant in snorkeloos. If a homozygous dominant snorkeloo marries a homozygous recessive snorkeloo, what are the expected genotype and phenotype ratios for their babies?

28. Other Inheritance Patterns • Incomplete Dominance • Codominance • Multiple Alleles • Polygenic • Sex-Linked (X linked)

29. Incomplete dominance • Hybrid is a blend of traits • Example: RR=red RR’ =pink R’R’=white Pink Carnation

30. Practice problem • A cross between red snapdragons and white snapdragons produces all pink offspring. • Show the cross of the F1 generation (cross two pink ones.) • What is the genotype ratio? • What is the phenotype ratio?

31. Codominance • Codominance—showing both alleles at the same time • Ex. *Checkered chicken (Black and white at same time) • B= Black W= White • So BB= Black, WW =white, and BW = black and white checkered. • Another example is Blood Type! • Type AB

32. Codominance x BB WW BW

33. Practice problem • Background: A black rooster and a white hen have offspring that are all checkered. • What inheritance pattern is this? • Cross a heterozygous chicken with a white chicken. • Give genotype and phenotype ratios.

34. Multiple Alleles • Multiple alleles: more than 2 possible alleles for a gene. Ex: human blood types • 3 Alleles: IA,IB, i • TYPES: A = IAIA, IAi B = IBIB , IBi AB = IAIB O = ii

35. Practice problem • Show the cross of a man heterozygous for type B blood with a woman that has type O blood • Describe genotypes and phenotypes of the offspring.

36. Polygenic traits • Polygenic trait = a trait that is influenced by more than one gene. • Ex. Eye color, skin color, hair color, height… • What do all of these characteristics have in common that can help you to recognize that the trait is polygenic?

37. Determining Sex (gender) • Look at sex chromosomes (X and Y) • XX = female • XY = male

38. Sex-Linked • Gene is found on a sex chromosome (usually X) • Trait more commonly seen in males. Ex. Colorblindness, hemophilia • Possible genotypes • Female= • XRXR • XRXr • XrXr • Male= • XRY • XrY “Y” is empty Fruit Flies C:\Documents and Settings\BBAUGHMAN\Desktop\bio powerpoints\Chapter 12 BDOL IC

39. Practice problem • A female carrier of colorblindness marries a normal male who is not colorblind. Describe their potential offspring in terms of genotype an phenotype probabilities.

41. Pedigree Charts • Male = • Female= • Sexual Union= • Offspring= • Shaded= has the trait (the phenotype)

42. Pedigree Chart -Cystic Fibrosis

43. end

44. Mendel’s Monohybrid Crosses • 1st Generation: All plants were tall • 2nd Generation: Mendel allowed tall plants of first generation to self-pollinate • 1000 plants produced in second generation What do you think Mendel saw in the F2 generation? • 1000 plants produced • 750 were tall • 250 were short • 3:1 ratio • The Short Trait Reappeared!!!

45. Mendelian Genetics • Mendel did several similar crosses looking at various traits of the pea plant • Each trait had similar results • One pair of the trait disappeared in the F1generation • The trait would reappear in the F2 generation WHAT DOES THIS MEAN?????

46. Rule of Unit Factors • 2 factors control each traits of an organism • These factors are genes located on chromosomes • Different gene forms called Alleles • Ex: tall allele (T), short allele (t) • Plant can have allele (TT), (tt) or (Tt) • Each allele is inherited from each parent; one from mom and one from dad

47. Rule of dominance • When Mendel crossed tall plants with short plants he observed only tall plants were produced in the F1 generation. • Dominant: observed trait • Mendel concluded allele for tall plants is dominan to allele for short plants • Dominant trait seen when allele is (TT) or (Tt) • Recessive: trait that dissappeared • Recessive trait only seen when allele is (tt)

48. Rule of dominance Dominant trait is always written with an uppercase letter Ex: tallness (T) Recessive trait is always written with a lowercase letter (t)

49. Law of Segregation • Mendel’s Law of Segregation • Recall, where there any short plants when Mendel crossed a tall plant with a short plant? • All plants in the F1 generation were Tall • When F1 tall plants were bred the shortness trait reappeared • Mendel concluded each tall plant in the F1 generation carried one dominant allele for tallness and one unexpressed recessive allele for shortness

50. Law of Segregation • Law of segregation: because each plant has two different alleles, it can produce two different types of gametes. • During fertilization, male and female gametes randomly pair so there can be a combination of four different alleles • (T1 T2) (T1 t2) (t1 T2) (t1 t2)