Standard 3 Genetics (Heredity)

1. Standard 3 Genetics (Heredity) The study of how genes are passed from Generation to Generation!

2. Vocab Review • Allele: alternate form of a gene: • Zygote: diploid cell that forms when the sperm and egg unite during fertilization (A or a) • Homozygous(same): Homo (same) zygous (allele) (AA or aa) • Heterozygous(different): (Aa) • Phenotype(appearance): (green or yellow) • Genotype (genetic makeup): (AA, Aa, aa) • Gamete: sex cell (egg/sperm)

3. Vocab Review • Purebred: A type of organism who’s ancestors are genetically uniform • Hybrid: offspring of two animals or plants of different breeds, varieties or species. (mule) • Crossing Over:Exchange of chromosome segments during meiosis I • Chromosome Map: Diagram that shows the locations of the genes on a chromosome • Polygenic Trait: Trait controlled by more than one gene

4. Gregor Mendel (1822-84) • Father of Genetics • Austrian Monk, spent his life working with traits of Pea Plants • Traits passed in “factors” from Generation to Generation • Working during the same time period as Darwin • He didn’t know what aGENEwas

5. Mendel’s Conclusions Law of independent assortment :different genes pair up randomly, unless they are on the same chromosome. (ex: dad’s eyes & mom’s hair color) Law of Dominance: traits have 2 alleles (one dominant “A” & one recessive “a”) Law of segregation :chromosome pairs separate during Meiosis (sperm and egg)

6. Aa Aa SPERM EGG a A A a Aa Zygote Law of Segregation (Meiosis) • A Heterozygous parent can produce Recessive or Dominant gametes (sperm/eggs)

7. Dominant Allele • Represented by a Capital letter “A” • Over powers or covers up the recessive • FULLY EXPRESSES THE PROTEIN EX:Brown Eyes Recessive Allele • Represented by a lower case letter “a” • Is covered up by the other allele • No/ Little protein is expressed EX:Blue Eyes

8. Probability • The likelihood that an event will occur • Probability = # of one kind of possible outcome total # of all possible outcomes When the word or is used you add the odds. So, 1/6 + 1/6 = 2/6 When the word and appears you multiply the odds. So, 1/6 x 1/6 = 1/36

9. Probability • What is the probability of rolling a 6 on a die? • 1/6 • What is the probability of rolling a 6 or a 5 on a dice cube? • 1/6 + 1/6= 2/6 • What is the probability of rolling a 6 and a 5 • 1/6 x 1/6= 1/36

10. 6 steps to solving a problem Genetics problems require the same 6 steps! • Identify Dominant and Recessive Phenotypes T=Tall t=Short • Parent phenotype x parent phenotype tall x tall • Parent genotype x parent genotype Tt x Tt • Punnett Square • Phenotypic ratio 3 tall: 1 short • Genotypic ratio 1:2:1 TT:Tt:tt

11. Mendel’s Generations • P = parent • F1 = offspring • F2 = offspring of F1

12. Dihybrid Crosses • Two Traits • Created by Mendel to test Laws of Independent Assortment and Segregation

13. Cross 2 plants that are heterozygous for the 2 traits (seed shape & pod color) Sample #1: Pea Plants R = round seeds r = wrinkled seeds G = green pods g = yellow pods • Identity Dominant and Recessive • Parent phenotypes • Parent genotypes • Sperm or Eggs (FOIL) • Punnet square • Possible Phenotypes • Phenotypic ratio

14. FirstOuterInnerLast RrGg STEP 4

16. Pp Pp Pp Pp Review Problem: Dominant/Recessive • In pea plants, purple flowers (P) are dominant over white flowers (p) show the cross between a purple plant and a white plant. P P GENOTYPES: - PP (0); Pp (4); pp (0) - ratio 0:4:0 p p PHENOTYPES: - purple (4); white (0) - ratio 4:0

17. Pp Pp pp pp Review Problem: Dominant/Recessive • In pea plants, purple flowers (P) are dominant over white flowers (p) show the cross between a purple plant and a white plant P p GENOTYPES: - PP (0); Pp (2); pp (2) - ratio 0:2:2 p p PHENOTYPES: - purple (2); white (2) - ratio 2:2

18. What do you do if you don’t know the genotype of the dominant parent? Testcross!!!!

19. TEST CROSS • A test cross is used to determine the genotype of a dominant trait. • (A dominant trait can be either homozygous dominant or heterozygous.) • The unknown trait is crossed with the recessive trait. • If any offspring show the recessive trait, the dominant parent had to be heterozygous.

20. RR = red rr = white Rr = pink Incomplete Dominance • A cross between organisms with two different phenotypes produces offspring with a third phenotype REDFlower x WHITE Flower ---> PINKFlower (Flower Color in 4 O'clock’s or Snapdragons)

21. GENOTYPES: R R 0:4:0 RR-Rr-rr r r Rr Rr Rr Rr Problem: Incomplete Dominance • Show the cross between a red and a white flower. PHENOTYPES: 0:4:0 Red/Pink/white

22. GENOTYPES: R r 1:2:1 RR-Rr-rr R r RR Rr Rr rr Problem: Incomplete Dominance • Show the cross between a red and a white flower. PHENOTYPES: 1:2:1 Red/Pink/white

23. Practice Problem A cross between a blue blahblah bird & a white blahblah bird produces offspring that are silver.  The color of blahblah birds is determined by just two alleles. • What are the genotypes of the parent blahblah birds in the original cross? • What is/are the genotypes of the silver offspring? • What would be the phenotypic ratios of offspring produced by two silver blahblah birds?

24. Co-dominance and Multiple Alleles And other kookie crosses!

25. INIS = both ISIS = sickle cells ININ = normal cells Codominance • meaning of the prefix "co-" is "together • The heterozygous condition, both alleles are dominant and expressed equally • “I” Represents the Blood Cells • Alleles are both represented by Capital Letters • Sickle Cell Anemia in Humans • N= Normal S: Sickle Cells sick

26. GENOTYPES: - ISIS (0) ININ (2) INIS (2) - ratio 0:2:2 ININ ININ PHENOTYPES: INIS INIS • Sick (0);carrier (2); normal (2) • - ratio 0:2:2 Problem: Codominance • Show the cross between an individual with sickle-cell anemia and another who is a carrier but not sick. IN IN IN IS

27. Multiple Alleles • There are more than two alleles for a trait • Blood type in humans • Blood Types • Type A, Type B, Type AB, Type O • Blood Alleles • A, B,O

28. Rules for Blood Type • A and B are codominant • IAIA = Type A • IBIB = Type B • IAIB = Type AB • A and B are dominant over O • IAi = type A…(AO) • IBi = type B…(BO) • ii = type O

29. The blood types differ due to the molecules that are present on the outside of RBC

30. IAi IAi IBi IBi Problem: Multiple Alleles • Show the cross between a mother who has type O blood and a father who has type AB blood. i i GENOTYPES: - AO (2) BO (2) - ratio 1:1 IA IB PHENOTYPES: - type A (2); type B (2) - ratio 1:1

31. IBi IAIB IAi ii Problem: Multiple Alleles • Show the cross between a mother who is heterozygous for type B blood and a father who is heterozygous for type A blood. IA i PHENOTYPES: IB i • Type AB IAIB • type B IBi • type A IAi • type Oii • ratio 1:1:1:1

32. Polygenic Traits • Traits determined by the combined effect of more than one pair of genes • EX: human height • Combined size of all of the body parts from head to foot determines the height of an individual • Different parts, are made by different genes

33. Sex-linked Traits • A trait that is determined by a gene found only on a sex chromosome • Females, are XX and have two alleles for genes that are on the X chromosome • Males, who are XY, only have one allele • For recessive traits, women that are heterozygous are said to be carriers

34. Red-Green Color Blindness • recessive genetic disorder • a condition that impairs a persons ability to distinguish between shades of red and green. • Does not otherwise effect vision • 16x more prevalent in men, rarely seen in women.

35. What do you see?

36. Ychromosome doesn’t carry an allele X- Linked Genetics • Studies by T.H. Morgan in Fruit Flies • 1,098 human X-linked genes • Colorblind • Hemophilia C=Normal Vision c= Colorblind

37. XC XC Xc XCXc XCXc Y XCY XcY Cross and a women with normal vision and a man that is colorblind 2 Carrier Females 1 Normal Male 1 Colorblind Male

38. Sex Limited • Only expressed in the presence of sex hormones • Female: estrogen • Male: testosterone • Only expressed in one of the sexes. • Beard growth in Men • Breast milk in Women

39. Sex influenced Traits • Expressed in both sexes • Expressed differently based on the sex (gender). • Baldness • Traits are influenced by their environment • In the presence of testosterone, the allele is dominant, but in the presence of estrogen the allele becomes recessive. • Therefore a woman can only be bald if she has two recessive genes for Baldness.

40. Environment Influences Traits • Height in humans • Prenatal health • Diet • Illness • Gender of Alligators and Rabbit fur color • Enzymes that create differences are only produced at certain temperatures

41. Human Genetics

42. Tracking Traits in Families Pedigrees A “family tree” drawn with standard genetic symbols, used to study human heredity

43. Females are represented with a circle Males are represented with a square

44. Mating is represented with a line connecting a square and circle

45. Children are represented with another connecting line

46. Children are put in order of birth from left to right

47. Connecting Pedigree Symbols Examples of connected symbols: • Fraternal twins • Identical twins

48. Affected or Not? • Un-shaded means they are not affected with the disorder • Completely Shaded means they have the disorder Disorder Normal Normal Disorder

49. What about the carriers? • In pedigrees, we use people with the disorder or trait to figure out who carriers the gene and who is normal for traits. aa AA Aa

50. Recognizing patterns in pedigrees Recessive or Dominant Trait? • If dominant, every affected individual will have a parent with the disorder • If recessive, an affected individual can have normal parents Recessive Dominant