GENETICS

1. GENETICS

2. The Blended Hypothesis: the traits from 2 parents are mixed to become a third trait. How traits are inherited: The debate in the 1800’s The Particulate Hypothesis: the traits from 2 parents are joined but remain discrete, and can be separated again to their original forms. Which hypothesis seems more logical to you? -Write your response down in your notes & give one supporting argument sentence.

3. In order to test these 2 hypotheses, a scientist must have “true breeding parents” What does “true-breeding” mean? The parent organism produces only one type of offspring for a particular characteristic

4. The blended hypothesis Parental generation F1 generation True breeding black coffee True breeding white cream The traits from two parents are mixed to become a third trait.

5. F1 generation F2 generation What type of offspring can the parents in the testcross make? Only mocha colored; one phenotype What type of offspring can the F1 generation create? Mocha-colored offspring; only one phenotype Can the 2 traits for the characteristic of color be separated out again in this example? No

6. Do we see examples of this type of character blending in real life?

7. The particulate hypothesis True breeding yellow True breeding red Parental generation F1 generation The traits from the two parents are joined but remain discrete, and can be separated again to their original forms.

8. F1 generation What type of offspring can the parental generation make? Only two-colored offspring; one phenotype possible What type of offspring can the F1 generation create? Yellow, red, or a mixture of red and yellow; 3 phenotypes are possible Can the 2 traits for color be separated out again in this example? Yes

9. Do we see examples of this type of character mixing in real life?

10. Which hypothesis, do you think, is more likely to be accurate? The particulate hypothesis could give just one type of offspring, which could account for why we see some blended traits, but with the blended hypothesis, traits could never separate out to yield variation in subsequent generations, as with discrete traits.

11. MONOHYBRID CROSSES PREDICTING PROBABILITY OF POTENTIAL OFFSPRING

12. All organisms pass on inherited information using haploid gametes. • Chromosomes are discrete packages of genetic material that can be traced back to the two parents that produced the zygote

13. The marbles in this example represent certain traits or alleles. Where are these alleles located (in us)? • They are located at specific places on paired chromosomes, called • genes. • One chromosome in a pair has Mom’s allele at a gene locus & the • other chromosome in the pair has Dad’s allele at the same gene locus. • Because the alleles come from different parents, they may not be the • same.

14. The zygote grows by mitosis to become a multi-cellular organism • How do inherited alleles from your parents show themselves in physical traits all over your body? Because DNA replicates before cell division, the alleles from each parent are passed on to every cell that makes up your body and thus the chromosomes can express any trait that is needed in any part of the body.

15. How do these inherited traits get passed on to your offspring? • One of these cells with all of Dad’s chromosomes and all of Mom’s chromosomes will become a gamete-producing cell in the gonads and begin making sperm and eggs with half the number of required chromosomes.

16. Which chromosomes will your children get- the ones from your dad or the ones from your mom? • They will get a random mixture of both as a consequence of crossing-over and the law of segregation.

17. Do you know the following terms? • Genotype • Phenotype • Dominant • Recessive • Test cross The alleles of a given gene locus; genetic make-up The expression of gene locus; observable trait An allele that is fully expressed in a heterozygote An allele that isn’t expressed at all in a heterozygote Breed an organism of unknown genotype with a recessive homozygote

18. Crossing pea plants for the color of flower Name the phenotypes of the flowers in the P generation Name the genotype of the flower in the F1 generation Which of the traits are dominant and which are recessive?

19. What are the possible gametes of parents of each of the following genotypes? AA Aa aa A or A A or a a or a

20. TEST CROSS

21. Let’s work out a problem with dogs… Heterozygous parents for black hair are crossed and their progeny are then test-crossed. Determine the expected genotypic and phenotypic ratios among the test cross progeny. B b Parental generation: Bb x Bb. Test cross of the F1 is to a white haired dog (bb). B b ¼ of the F1 will be black haired homozygous dominant. When crossed with bb the result will be all black (Bb). ½ of the F1 will be black haired heterozygous (Bb). When crossed with bb the result will be ½ black and ½ white. ¼ of the F1 will be white haired (bb). When crossed with bb all offspring will be white haired So… ½ Bb and ½ bb ratio= 1:1 for phenotype and 0:1:1 for genotype

22. Recall the Law of Independent Assortment

23. Punnett square examples Look over worksheets

24. Probability • If a coin is flipped once, what is the probability it will land on heads? • If it lands on heads, what is the probability it will land on heads again? • If I keep flipping the coin and it keeps coming up heads, will that affect the probability of the outcome of my next flip?

25. What is the probability that I will get heads on 2 coin tosses in a row? • This changes the probability because you are now asking for the probability of flipping heads and flipping heads again. • When you have 2 separate probabilities that both must occur, the 2 separate probabilities must be multiplied to find the overall probability. So the probability of heads and heads occurring is ½ x ½ = ¼

26. The rule of multiplication • Used whenever there is a statement of one probability “and” another probability Let’s practice: • What is the probability that a couple would have 3 boys? • What is the probability that parents with the genotypes Aa and Aa would have a child with the genotype AA? ½ x ½ x ½ = 1/8 Probability of dad giving “A” is ½ and the same can be said for mom then… ½ x ½ = ¼

27. Let’s try another!!! Black wool in sheep is recessive (w) to white wool which is dominant (W). A white ram is crossed with a white ewe. Both parents carry the allele for black (w). They produce a white ram lamb which is then back crossed to the female parent. Determine the probability of the back cross offspring being black. The white ram lamb (F1) is either WW or Ww. 1/3 of the white offspring (WW) crossed with parent Ww will result in zero black lambs W w W 2/3 of the white offspring (Ww) crossed with parent Ww will result in ¼ black lambs. w So… 1/4 x 2/3 = 1/6 or 0.16

28. Let’s use a deck of cards (52 cards) • If the probability of getting dealt an ace from a deck of cards is 4 out of 52, what is the probability of being dealt an ace or a king? • The probability of getting an ace is 4/52 and the probability of getting a king is 4/52. You must add the probabilities together to get the total probability. • 4/52 + 4/52 = 8/52

29. Rule of addition • Used whenever there is a statement of one probability “or” another probability. Let’s practice: • What is the probability of being dealt an ace or a face card from one deck of cards? • The probability of getting an ace is 4/52 & the probability of getting a face card is 12/52 So… 4/52 + 12/52 = 16/52 = 4/13

30. Dihybrid crosses

31. IIGG x iigg I = inflated i= constricted G= green g= yellow How many traits or genes are represented by these genotypes? When gametes are made in meiosis, how many alleles does each gamete get of a single gene? What gametes can the 1st parent make? What gametes can the 2nd parent make? What type(s) of offspring will be produced? If the F1 generation was allowed to cross, what types of gametes would result? 2 – pod texture & pod color One allele of each gene IG ig IiGg = F1 generation “IG” “Ig” “iG” and “ig”

32. If both parents are heterozygous (IiGg x IiGg) • How can we predict the outcome? Creating a dihybrid cross!!!

33. Recall the law of segregation: • Do both dominant alleles have to go to the same gamete? • Can a gamete have a mixture of dominant and recessive alleles? • Do you have a mixture of dominant and recessive traits from your parents? • How is it that each gene can segregate independently when they are all on a limited number of chromosomes? No Yes Yes Crossing over during prophase 1 allows alleles to mix randomly as the gene loci are not located too near one another on the chromosome

34. GENE EXPRESSION

35. How does a genotype result in a phenotype? • The genotype is an abbreviation for the allele found at a specific gene. • The gene is a sequence of DNA that codes for the “recipe” to make a particular protein. • For example” melanin gene locus can have different sequences of DNA (different alleles) that either make melanin – a dark skin pigment that absorbs UV or don’t.

36. If the genotype is “MM” then the person has 2 alleles, or strands of DNA, that make the protein melanin. • If the genotype is “Mm” then they have one allele that makes the protein & one that doesn’t • Which genotype would make the darker skin?

37. Let’s look at Snap Dragons CR CR CWCW What color would a snap dragon be with a genotype of CR CW ? THIS IS AN EXAMPLE OF INCOMPLETE DOMINANCE

38. Gene expression • Alleles do not have to be completely expressed or unexpressed. • An allele can make small amounts of a protein in its recessive form and greater amounts in its dominant form. • There is a wide range of expression for any allele termed dominant or recessive.

39. CODOMINANCE- neither of the 2 alleles of the same gene totally masks the other. The result is a combination of both dominant traits.

40. CODOMINANCE R = red colored coat W= white colored coat RR x WW R R All offspring will be …..? RW RW W RED & WHITE !! W RW RW

41. Blood Types • There are 6 genotypes. • They make up 4 phenotypes (blood types). • A and B are codominant, and O is recessive. A A B B AB O

42. What are the possible blood types of the potential children of an AB (IAIB) male and an B (IB i) female? What % chance will the offspring be type B? Hint: use a punnett square

43. What are the possible blood types of the potential children of anAB (IAIB)male and anB (IB i)female? IAIB x IBi IA IB TYPES: A, B, or AB IB What % chance will the offspring be type B? i 50%

44. PEDIGREES Collecting information about a family ‘s history for a particular trait and creating a family tree that displays how the trait is passed down from generation to generation.

45. One type of pedigree shows only the phenotypes of individuals.

46. Another type of pedigree chart gives information about all of the individuals’ genotypes for a trait.

47. Addams Family Bb bb Bb bb bb Bb Bb bb B_ What is the percent chance the new Addams’ baby will have web feet?

48. Using pedigrees to trace inheritance patterns WS When you are done with the WS, get together with your lab groups and come up with 3-4 rules that apply to recessive allele inheritance patterns and 3-4 rules that apply to dominant allele inheritance patterns.

49. Possible Rules for Inheritance Patterns Recessive Dominant Affected offspring must have at least one affected parent The phenotype appears in every generation without skipping Two unaffected parents have no affected offspring • Unaffected parents can have affected offspring • The phenotype can skip a generation • Individuals with no sign of the allele can be carriers

50. Genetic Testing