Patterns of Heredity

1. Patterns of Heredity

3. Not • ______ all traits are simply inherited by dominant and recessive alleles (Mendelian Genetics). In some traits, neither allele is dominant or many alleles control the trait. There are different ways in which traits can be inherited from parents to offspring.

4. 5 Different Modes of Inheritance

5. 1. Incomplete Dominance • Definition: • Neither allele for a gene ____________. • Phenotype of the heterozygous offspring will be a ________ of the two homozygous parents. dominates blend

6. Incomplete Dominance homozygous • Ex. A _____________ white flower crossed with a _____________ red flower will produce all _______________ pink flowers. homozygous heterozygous

7. Incomplete Dominance • NOTATION: • Alleles are all capital letters because NEITHER one ____________ the other. So one of the alleles has a ________ (‘) on it to represent an alternate expression of the gene. dominates prime

8. KEY • Always make a _____ to show the genotypes and the resulting phenotypes. • Still supports Mendel’s Law of Independent Assortment.

9. Ex. 1) • In a certain species of snapdragons, the combined expression of both alleles for flower color produces a new phenotype – pink. A red snapdragon is homozygous and is crossed with a homozygous white snapdragon. What are the genotypic and phenotypic ratios of this cross?

10. Key: Red = RR White = R’R’ Pink = RR’ P cross = RR x R’R’ G: __________ P: __________ 100% RR’ RR’ RR’ 100% Pink RR’ RR’

11. Ex. 2) • Then cross the F1 generation and what are the genotypic and phenotypic ratios of this cross?

12. Key: Red = RR White = R’R’ Pink = RR’ P cross = RR’ x RR’ G: __________ P: _____________ 1RR:2RR’:1R’R’ RR’ 1Red:2Pink:1White RR’ RR’ R’R’

13. 2. Codominance • Definition: • Both __________ are expressed __________ alleles EQUALLY

14. Codominance • Phenotypes of heterozygous offspring are showing both traits! • Ex. Red cows crossed with white will generate roan cows. _______ refers to cows that have red coats with white blotches. Roan

15. Codominance • NOTATION: • Two ____________ alleles (capital letters) are used. • Always make a _____to show the genotypes and the resulting phenotype. different KEY

16. In chickens, black-feathered is not wholly dominant over white-feathered, so heterozygous chickens are black and white checkered. Cross two heterozygous chickens. What would the appearance of their offspring be?

17. Key: Black = BB White = WW Checkered = BW 1 Black 2 Checkered 1 White BB BW BW WW P cross = BWxBW Phenotype:

18. In shorthorn cattle, the hybrid between red and white is called a roan. What phenotypes would result in the cross of a roan and a white?

19. Key: Red = RR White = WW Roan = RW RW 2 Roan: 2 White WW RW WW P cross = RW x WW Phenotype

20. 3. Multiple Alleles • Definition: • More than ______________ for a single gene can control a trait. • Multiple alleles must be studies by looking at the entire population of species. two alleles

21. Multiple Alleles • Each individual carries only two alleles for any gene (one on each homologous chromosome). • In this form of inheritance, a trait can have one gene, but ______________ for that gene. 100 alleles

22. Multiple Alleles • Ex: The human blood group can be any combination of A, B, and O.

23. Multiple Alleles • The alleles are IA, IB and i. • Alleles ___ and ___ are ________________. • Alleles ___ (“O”) is ____________. A B CODOMINANT RECESSIVE i

24. NOTATION: • The possible genotypes/phenotypes.

25. Multiple Alleles • NOTE: the “i” is dropped from the genotype of A and B when the ____________ is written. • (Genotype IAI is type A blood) phenotype

26. Interesting Fact • In the US, about 45% of the population is type O, 42% type A, 10% type B and only 3% type AB.

27. The ABO Blood System

28. The positive and negative of a blood type is called the ____________, it is totally a separate _______ with RH+ (RR or Rr) and Rh- alleles (rr). • If you have the protein = Rh+ • If you DO NOT have the protein = Rh- Rh factor gene

29. Interesting Fact • In the US, about 85% of the population is Rh+ and 15% Rh-. • Thus the chances of someone being O- (having both ii and rr) would be 45% X 15% = 6.75%.

30. The most rare blood type would be ______, about 0.45% if the population. _____ is the universal donor. _____ is the universal recipient. AB- O AB

31. 2 IAi : 2 IAIB IAi IBi 2 Type A: 2 Type B IAi IBi P cross = IAIB x ii Genotypes: Phenotypes:

32. A father is homozygous blood type A and the mother is heterozygous blood type B, what could be the possible genotypes and phenotypes of their offspring's blood types?

33. 2 IAi : 2 IAIB IAIB IAIB 2 Type A: 2 Type AB IAi IAi P cross = IAIA x IBi Genotypes: Phenotypes:

34. Two Types of Chromosomes Sex chromosomes 1. _____________________: last pair of chromosomes - 23rd pair for humans. XX = _________ XY = _________ female male

35. Two Types of Chromosomes Autosomal chromosomes 2. _________________________ or ___________ • All other pairs of chromosomes – 1st – 22nd pairs in humans. Autosomes

36. 4. Sex-Linked Traits (X-Linked) • Other genes besides the alleles for sex are located on the sex chromosomes.

37. Definition: • Those traits will occur _______ frequently in males than females, such as color blindness and hemophilia. MORE

38. Why? • Alleles on a gene may be present on the X chromosome but _________ on the Y. These are called sex-linked traits. absent

39. This means that ________ may inherit ______ allele for a characteristic and that allele will be expressed, whether it is dominant or recessive, because it is the _______ allele present on their X chromosome. males one only

40. X-Linked traits most likely will be ____________ to the normal condition and the Y chromosome lacks the gene for a trait, so males have a higher chance of having the disorder. RECESSIVE

41. These traits generally do NOT show up in __________ since females have genes on both their X chromosomes. females

42. Notation: • The alleles for these traits are written as ______________ on the ___ chromosome ONLY. superscripts X

43. No • ______ alleles are written on the Y chromosome! • Ex: Colorblind male = XbY Normal male = XBY _______________ FEMALES are known as __________ XBXb Heterozygous carriers

44. Ex. 1) Color blindness is a sex-linked trait that is caused by a ______________________. A colorblind man marries a woman that is homozygous for normal vision. recessive allele

45. What possible types of vision could be found if they had boys? __________ Normal What possible types of vision could be found if they had girls? __________ XNXn XNXn Normal XNY XNY P cross = XNXN x XnY

46. Ex. 2) A girl of normal vision, whose father was colorblind, marries a colorblind man. What types of vision could be found in their children?

47. What types of vision could be found in their children? 50% Normal visionand 50% colorblindness. XNXn XnXn XNY XnY P cross = XNXn x XnY

49. 5. Polygenic Inheritance • Traits are determined by ___________________. • They may or may not be found on the same chromosome. • Each gene may have more than 2 alleles. MANY genes

50. The phenotypes may vary depending on the number of dominant and recessive alleles in the genotype.