PROBABILTY

2. PROBABILTY • P= number of ways that a given outcome can occur total number of possible outcomes

3. Gene Interactions There are three main types of gene interactions: 1) Multiple Alleles There are many traits that are controlled by more than two alleles for example, eye colour in Drosophila is controlled by four possible alleles. The following phenotypes and dominance hierarchy is possible: wild type (red) > apricot > honey > white

4. Multiple Alleles • Wild type- the most commonly seen trait • Mutant- non-wild-type traits

5. When dealing with multiple alleles, it is no longer necessary to use upper & lower case letters both letters & upper case numbers are used. phenotype genotype wild type E1 Apricot E2 honey E3 white E4 Predict the genotypes and phenotypes of the F1 generation from the mating of wild type (E1E4) with apricot (E2E3).

6. Predict the genotypes and phenotypes of the F1 generation from the mating of wild type (E1E4) with apricot (E2E3). E1 E4 E1E2 E2E4 E2 E1E3 E3E4 E3 In the F1 generation ½ are wild type; ¼ apricot; ¼ honey

7. Do Now phenotype genotype wild type E1 Apricot E2 honey E3 white E4 With the above information, make two heterozygous crosses what phenotypes do you get?

8. 2) Incomplete Dominance In some heterozygotes, both alleles of a pair are expressed in the phenotype. These alleles are said to be equally dominant. This lack of dominance is known as incomplete dominance. eg. P1 Black  White F1 Grey P2 Grey × Grey F2

10. Ex. Snapdragons An interaction between the alleles in the heterozygote shows an intermediate phenotype. WW Ww ww

11. 3) Codominance A form of incomplete dominance where two alleles are expressed in such a way that the effect of each is noticed separately in the phenotype. Both parental phenotypes can be distinguished in the heterozygote offspring.

12. The expression of one allele does not mask the expression of another. Ex. A red bull crossed with a white cow = roan calf (calf has intermingled white & red hair)

13. Roan cattle and horses have both coloured and white hair. Blue Roan Strawberry Roan

14. The ABO blood group system is another example. Inheritance of blood groups is determined by the gene “I” which has three different alleles, only two of which can occur at the locus at once. The alleles are responsible for producing antigens on the surface of the red blood cells, which determines the blood group. Alleles A and B are co-dominant so that when they are both present, both A and B antigens are produced. Both A and B are dominant to O.

15. Blood Types (A, B, O, AB) Allele IA – formation of blood factor A (antigen A) Allele IB – formation of blood factor B (antigen B) Allele I – no factors result Genotype Blood Type IAIA or IAi A IBIB or IBi B ii O IAIB AB

16. Type A Type B Type AB Type O IA an IB are codominant and i is recessive. Rh antigens are straight dominant vs. recessive.

17. Blood types of North America Blood types of North America with RH.

18. Example: A mother with blood type A has a child with Blood type O. The father is blood type B. Indicate the genotypes of the parents. Father can be IBIB or IBi and mother can be IAIA or IAi. To have a child that is type O (ii) both mother and father must contribute the i allele, therefore the father must be IBi and the mother is IAi

19. Case Study • Page 611: A Mystery of Blood Types

22. Pedigrees • A chart or register showing a line of ancestors • Circles represent females, squares represent males, solid circles & squares represent those who have the trait being studied. • Horizontal lines between circles and squares represent mating between male and female. • A vertical line joins parents and children. • Pedigrees are often used to study sex-linked traits such as color-blindness and hemophilia

24. PEDIGREE SUMMARY This will help you determine a trait in a pedigree as with autosomal or X-linked: Autosomal Dominant • must be in each generation • affected individuals transmit to minimum ½ of their offspring • males and females are equally affected • cannot have carriers, they will all be affected!

25. Autosomal Recessive • may skip a generation • affected offspring generally have normal (but heterozygous) parents • male and female are equally affected

26. X-linked Dominant • very likely to be observed in each generation • females pass on to half of either sex • no transmission from father to son (only daughters) X-linked Recessive • affect males more than females • no transmission from father to son • daughters of males are carriers • females pass onto ½ sons • affected females have affected fathers and carrier mothers

28. Pedigree analysis

29. Probability • Probability is the likelihood of an event happening. • Probability can be expressed by the following formula: Probability = # of chances for an event # of possible combinations

30. Therefore, when a coin is tossed, there are two possibilities – heads or tails. What are the chances of getting heads? What is the probability of two coins being tossed and getting heads? Coin 1 – Coin 2 – 1 head/2 head/tail = 50 % chance ½ = 50 % chance ½ = 50 % chance

31. The Rule of Independent Events – Product of the probabilities of two separate events: The Product Rule – Chance has no memory. This means that previous events will not affect future events. Ex. If you tossed two heads in a row, the probability of tossing heads again will still be ½. ½ × ½ = ¼ therefore a 25% chance The probability of two or more independent events occurring together is the product of the individual probabilities if each individual event occurs separately.

32. Dihybrid Crosses Mendel also studied two separate traits with a single cross by using the same procedure he had used for studying single traits.

33. Mendel crossed a purebred yellow round pea with a purebred green wrinkled pea. Pure breeding round = RR Pure breeding wrinkled = rr Pure breeding yellow = YY Pure breeding green = yy Genotype for the yellow, round parent is RRYY Genotype for the green, wrinkled parent is rryy

34. P1 YYRR x yyrr Purebred yellow round × Purebred green wrinkled The entire F1 generation has the genotype: YyRr and is phenotypically yellow round! Male gametes Female gametes F1

35. Now let’s cross the F1 generations with one another and see what we get…

36. 9/16 Yellow Round 3/16 Yellow wrinkled 3/16 green Round 1/16 green wrinkled The phenotypic ratio 9:3:3:1 is the ratio you will find in all heterozygous dihybrid crosses!

37. Example: In summer squash, white fruit color is dominant “W” and yellow fruit color is recessive “w”. Another allele produces disc shaped fruit “S” while its recessive allele “s” yields sphere-shaped fruit. If a pure breeding white disc variety is crossed with a homozygous yellow sphere variety, the F1 are all white disc hybrids. If the F1 generation is allowed to mate, what would be the expected phenotypic ratio in the F2 generation? Try this!

38. P1 WWSS x wwss F1 All offspring will be WwSs P2 WwSs x WwSs F2

39. Rhesus Factor & Birth P1 : Female Rh- × Male Rh+ • Baby is Rh+ because father is. Mother’s blood produces antibodies upon birth, (since blood mixes at birth). First baby is okay. • Second pregnancy- mom’s antibodies can now move across the placenta and cause baby’s RBC’s to clump (agglutinate) if second baby is also Rh+. This decreases oxygen delivery in the baby – “blue baby.”

40. What can be done? • Mom can be given an injection of a drug that inhibits antibody production immediately after delivery. What happens if this is undetected? • Baby could be given a blood transfusion while in the womb. Fairly uncommon.

41. Blood Types & Rhesus Factor Question R – dominant allele (Rh+) r – recessive allele (Rh-) Example: A woman homozygous for blood type A and heterozygous for the rhesus allele, Rh+, has a child with a man with type O blood who is Rh-. What is the probability that their child will have blood type A, Rh+? There will be a 50% chance.

42. Do Now • Biology creatures have many strange traits. Blinking eyes “B” is dominant and burning eyes are recessive “b”. Another allele produces pleasant smelling pheromones “P” while its recessive allele “p” yields rotting fruit pheromones. If a pure breed blinking pleasant smelling biology creature is crossed with a heterozygous blinking pleasant smelling biology creature, what would be the expected phenotypic ratio?

43. Techniques used in order to produce the genotype or phenotype that you want: Selective Breeding: the crossing of desired traits from plants or animals to produce offspring with both characteristics

44. Inbreeding: the process by which breeding stock is drawn from a limited number of individuals possessing desirable phenotypes. Hybridization: Blending of desirable but different traits.

45. Gene Interaction 1) Many traits studied by Mendel were controlled by one gene. 2) Some traits are regulated by more than one gene; many of your characteristics are determined by several pairs of independent genes – polygenic. eg.) skin color, eye color and height, feather colour in parakeets 3) One trait controlled by more than one allele (multiple alleles). Eg. Blood types, Drosophilia eye colour

46. 4) Genes that interfere with the expression of other genes are called epistatic. Example: • allele B produces a black coat color in dog • b produces a brown coat color • A second gene, W prevents the formation of pigment • w does not prevent color

47. genotype wwBb would be black • genotype WwBb would appear white • W allele masks the effect of the B color gene • If wwBb is crossed with a WwBb, state the phenotypes produced. 8/16 = white 6/16 = black 2/16 = brown

48. 5)Complementary Interaction occurs when two different genotypes interact to produce a phenotype that neither is capable of producing by itself. Example: • Allele R produces a rose comb in chickens • Allele P (on a different chromosome) produces a pea comb. • R and P alleles both present = walnut comb • The absence of rose and pea alleles results in an individual with a single comb