Mendelian Genetics

1. Mendelian Genetics

2. Mendelian Genetics • Heredity – the passing of traits from parents to offspring • Genetics: The scientific study of heredity

3. Mendelian Genetics • Chromosomes- rod-shaped structures in the nucleus that transmits genetic information • Genes- units of hereditary information found on the chromosomes

4. Important Vocabulary • dominant- a gene that masks the expression of another gene in a pair (Symbol- capital letter) • recessive- a gene in a pair that is hidden by the dominant gene (Symbol- lower case letter) Parent 1 R = red dominant Parent 2 r = yellow recessive Offspring Red (Rr) dominant

5. Important Vocabulary • Homozygous- two genes in a pair that are identical. Ex. Homozygous dominant- RR GG Homozygous recessive- rr gg • Heterozygous- individual with one dominant and one recessive gene in a pair. Ex. Rr or Gg

6. Important Vocabulary Identify each of the pairs below as homozygous dominant, homozygous recessive, or heterozygous. Yy rr Tt SS  TT aa  Bb Ss Heterozygous Homozygous recessive Heterozygous Homozygous dominant Homozygous recessive Homozygous dominant Heterozygous Heterozygous

7. Important Vocabulary • Allele- each form of a gene for a certain trait . Ex. B = dominant allele (brown eyes) b = recessive allele (blue eyes)

8. Alleles = alternative versions of a gene

9. Important Vocabulary • Genotype- the pair of alleles represented by the capital and lower case letters. • Phenotype- the trait that is actually expressed in an organism Examples Genotype Phenotype YY yellow seeds Yy yellow seeds yy green seeds

10. Important Vocabulary • Examples of genotype and phenotype

11. Important Vocabulary • Examples of genotype of phenotype

12. Example Trait = Tongue Rolling R- a dominant allele that codes for muscles that help in tongue rolling r- is a recessive allele that does not code for that muscle This boy has at least one dominant allele in his 2 letter genotype. His phenotype is that he is a tongue roller

13. Figure 14.5 Genotype versus phenotype

14. Inheritance • You get your genes from your parents • In meiosis, half of the chromosomes in a pair come from the Dad, half come from the Mom • What we know today is based on the work of Gregor Mendel

15. 1822-1865 Gregor Mendel -Austrian Monk – pea plants in monastery garden – COUNTED the plants and compiled data (QUANTITATIVE APPROACH to science) Paper was published in 1866, but not enough was understood to truly value this work. Today known as father of modern genetics

16. Mendel chose to use plants that were true-breeding… • P generation – parentals; true-breeding (On their own create identical offsprings) parents that were cross-pollinated • F1 generation – hybrid offspring of parentals that were allowed to self-pollinate • F2 generation – offspring of F1’s

17. *Flower color : purple (P) vs. white (p) PP x pp All Pp PP, Pp & pp

18. Figure 11-3 Mendel’s Seven F1 Crosses on Pea Plants Section 11-1 Seed Shape Seed Color Seed Coat Color Pod Shape Pod Color Flower Position Plant Height Round Yellow Gray Smooth Green Axial Tall Wrinkled Green White Constricted Yellow Terminal Short Round Yellow Gray Smooth Green Axial Tall Go to Section:

19. Mendel’s 3 principles • Principle of Dominance- one factor (gene) in a pair may prevent the other factor (gene) in a pair from being expressed. P Parental Round RR Wrinkled rr RR F1 First Filial All Round Rr F2 Second Filial

20. Mendel’s 3 principles • Principle of Segregation- the members of each pair of genes separate, or segregate, when gametes are formed.

21. Mendel’s 3 Principles Principle of Independent Assortment- two or more pairs of genes segregate independently of one another during the formation of gametes In other words….. Just because a seed is round does not mean that it has to be yellow.

22. Mendel’s 3 principles • Principle of Independent Assortment R = round r = wrinkled Y = yellow y = green RrYy RY Ry rY ry Yellow Green Yellow Green Round Round Wrinkled Wrinkled

23. A Test Cross • Used to determine an unknown genotype of parents • (Works backwards) • ALWAYS CROSS UNKNOWN WITH RECESSIVE PHENOTYPE – Why?

24. Punnett Square • Device for predicting the results of a genetic cross between individuals of a known phenotype. • Example Character – flower color Alleles – Purple (P) and white (p) Note: Purple is dominant with a capital letter and white is recessive shown with a lowercase of dominant trait Genotypic combos possible – two dominants: PP (homozygous dominant) two recessives: pp (homozygous recessive) One of each: Pp (heterozygous)

25. One trait crosses – only one character considered Steps to do: • Write out genotypes of parents • Write out possible gametes produced • Draw 4 box Punnett square • Put one parent on the left side and one parent across the top • Fill in boxes • Determine genotypes by reading Punnett starting from top left • Determine phenotypes by reading from genotype list

26. Punnett Square Practice Violet flowers are dominant to white flowers. Diagram a Punnett Square for 2 heterozygous flowers. What is the parents’ genotype(s)? What is the parents’ phenotypes(s)? What is the genotypic ratio for the offspring? What is the probability of producing a white flower? (In percent) V v Vv violet VV Vv V v 1:2:1 Vv vv 25%

27. Punnett Square Practice Black rabbits are dominant over brown rabbits. A heterozygous male is crossed with a brown female. What is the mother’s genotype? What is the father’s genotype? Diagram a Punnett Square for this cross. What is the genotypic ratio? What is the phenotypic ratio? B b bb Bb Bb bb b b 1:1 Bb bb 1:1

28. Two-trait Crosses • Because genes separate independently we can determine the possible outcomes of a two-factor cross. • Example: Guinea pig hair color and length • B- black b- brown • S- short s- long F1 Hybrids for Hair Color and Length: BbSs FOIL – First, Outer, Inner, Last Possible gametes passed on to offspring: BS, Bs, bS, and bs –place in punnett square

29. Dihybrid Crosses BbSs x BbSs

31. Dihybrid Cross • Example: Watermelon color and shape • G- green g- striped • S- short s- long • Cross two Hybrids for Shape and Color: GgSs Gs gS GS gs GS GGSs GgSS GgSs GGSS Gs GGSs GGss GgSs Ggss gS GgSS GgSs ggSS ggSs GgSs ggSs ggss gs Ggss

32. Dihybrid Cross 9 • Now that the Punnett square is complete, determine the Phenotypic ratio GS Gs gS gs _______Green, short _______Green, long _______Striped, short _______Striped, long Therefore, the ratio is: _________________ 3 Green, short Green, short Green, short 3 Green, short GS Gs gS gs 1 Green, short Green, long Green, short Green, long 9:3:3:1 Green, short Green, short Striped, short Striped, short Green, short Green, long Striped, short Striped, long

33. Three-trait Crosses Mendel’s pea plants The shape of the pea is controlled by one set of alleles, where round is completely dominant to wrinkled: • RR = round • Rr = round • rr = wrinkled The second set of alleles in this example controls the color of the peas. Green is dominant to yellow: • YY = yellow • Yy = yellow • yy = green The third set of alleles in this example controls the shape of the pea pod. Smooth is completely dominant to constricted: • SS = smooth • Ss = smooth • ss = constricted

34. Three-trait Crosses Mendel’s pea plants • Cross RrYySs x RrYySs

35. Three-trait Crosses Mendel’s pea plants • Cross RrYySs x RrYySs • Genotypic ratio:1 RRYYSS:2 RRYYSs:1 RRYYss:2 RRYySS:4 RRYySs:2 RRYyss:1 RRyySS:2 RRyySs:1 RRyyss:2 RrYYSS:4 RrYYSs:2 RrYYss:4 RrYySS:8 RrYySs:4 RrYyss:2 RryySS:4 RryySs:2 Rryyss:1 rrYYSS:2 rrYYSs:1 rrYYss:2 rrYyss:4 rrYySs:2 rrYyss:1 rryySS:2 rryySs1: rryyss • Phenotypic ratio 27: round, yellow, smooth pod   9: round, yellow, constricted pod   9: round, green, smooth pod   3: round, green, constricted pod   9: wrinkled, yellow, smooth pod   3: wrinkled, yellow, constricted pod   3: wrinkled, green, smooth pod   1: wrinkled, green, constricted pod  

36. Beyond Dominant and Recessive • Incomplete Dominance One allele is not completely dominant over the other – something in the middle is expressed Ex. Red and White Snapdragons – Make Pink (Like mixing paints) Red – RR White – WW Pink – RW Only one phenotype for each one genotype

38. Codominance • Codominance Both alleles are expressed in the phenotype Ex. Cow Hair Color RR – Red WW – White RW – Roan (Red & White)

39. Incomplete Dominance Example: Flower color is an incomplete dominant trait. One red gene and one white gene produces a pink flower. • Cross two pink flowers.  1. What is the parents’ genotype? 2.What is the parents’ phenotype? 3. What is the genotypic ratio for this cross? 4. What is the phenotypic ratio for this cross? 5. What is the probability of producing a red flower? 6. What is the probability of producing a pink flower? R W RW Pink RR RW R W 1:2:1 1:2:1 RW WW 25% 50%

40. Beyond Dominant and Recessive • Multiple Alleles Genes have more then two alleles Ex. Blood Type Color Coats in Rabbits A and B are also codominant

41. More on blood types….. • The blood type determines what antibodies are located within the blood. Type A blood has type B antibodies. If type B blood is put into their bodies, their immune system reacts as if it were a foreign invader, the antibodies clump the blood - can cause death. • Type AB blood has no antibodies, any blood can be donated to them - they are called the "universal acceptors" • Type O blood has no surface markers on it, antibodies in the blood do not react to type O blood, they are called the "universal donors"

43. Blood types • Diagram a cross for a man with blood type AB and a woman with blood type O. What is the children’s genotype(s)? What is the children’s phenotypes(s)? What is probability of producing a child with blood type O? (in percent) What is the probability of producing a child with blood type B? (In percent) A B AO, BO Blood type A or B AO BO O O 0 AO BO 50%

44. Rh Factor - +/- • A second main trait for blood exists • Rh = protein on the surface of a red blood cell • Rh + means has protein/Rh- does not • Rh+ is dominant; Rh- is recessive

45. Blood Typing is Important Because… • Transfusions - Red blood cells of incompatible blood types may clump together leading to death – (agglutination) • Rh (–) person cannot take Rh(+) blood • O- universal donor; AB+ universal recipient • Solve problems of unknown parentage. • Unable to say who definitely is the father, but can say who definitely isn’t the father.

46. Blood agglutination

47. More Multiple Alleles Full color: CC, Ccch, Cch, Cc Chinchilla: cchcch, cchch, cchc Albino: cc Himalayan: chch, chc

48. Polygenic Inheritance • When a trait is controlled by 2 or more genes • AaBBCc • Explains the presence of multiple phenotypes for a single trait (Polymorphism) • Example: • Skin Color-if a darker skin and lighter skin individual produce offspring, the offspring will have an intermediate color of skin • Hair Color/Eye Color - there are approximately six genes that govern eye color, from brown to blue. • Height, nose length, and footsize to name a few…

49. At least three loci interact to produce a variety of fruit colors in these plants. • Y - timing of chlorophyll elimination (Y - early; y - normal) • R - color of carotenoid pigments (R - red; r - yellow) • C - regulation of carotenoid deposition (C - normal; c1, c2 - lowered concentration) Different combinations of alleles at the three loci produce multiple phenotypes: Y- rr c1c2 - pale yellow Y- rr Cc2 - darker yellow yy rr CC - green Y- R- CC - red yy Rr CC - purple Y- Rr Cc2 - pale yellow

50. Polymorphism – a widerange of trait values