Genetics, the oldest branch of Biology

1. Genetics, the oldest branch of Biology

2. Genetics = Information Flow Transmission Genetics = information flow between generations Molecular Genetics = information flow within cells/organisms DNA RNA  Protein

4. Data of Goss (1824) pea plant from green seed pea plant from yellow seed X All seeds yellow – grow and self fertilize Many pods with both yellow and green seeds Some pods with all yellow seeds – grow into plants and self fertilize Some pods with all green seeds Self fertilization of plants grown from green All progeny plants Have pods with green seeds only Some pods with all seeds yellow, some with green and yellow seeds

5. Data of Mendel (1866) pea plant from green seed pea plant from yellow seed X All seeds yellow - Grow into plants and self fertilize First filial generation (F1) second filial generation (F2) • Count # of green and yellow seeds: • 8023 total seeds • 6022 yellow • 2001 green – grown into plants: self fertilization yields • all green seeds Take 519 yellow seeds – grown into plants: self fertilization Of these 519 plants, 166 bred true (all yellow seeds), 353 did not (mixed yellow and green seeds)

9. Mendel’s model True breeding yellow AA True breeding green aa egg cells pollen cells fertilize a A x Aa (yellow seeds) – grow into plants and self fertilize F1 A a (pollen) 3:1yellow:green __________________ ¼ true breeding yellow ½ “impure” yellow ¼ true breeding green A F2 (eggs) a

10. Mendel’s First Law Each trait is governed by 2 particles*, one inherited from each parent. These two particles do not influence each other in any way within an individual, but separate, uncontaminated in any way, into gametes at the time of reproductive cell Formation. (an unstated corollary is that any pollen cell can fertilize any egg cell = random fertilization). Testing the law: - the test cross (Aa x aa) predicts new ratios - other traits tested *Introduce modern terms: dominant, recessive, alleles, phenotype, genotype, heterozygote, homozygote

12. Results of all Mendel's crosses in which parents differed for one character • Parental phenotype F1 F2 F2 ratio • 1 . Round X wrinkled seeds All round 5474 round; 1850 wrinkled 2.96:1 • 2. Yellow X green seeds All yellow 6022 yellow; 2001 green 3.01:1 • 3. Purple X white petals All purple 705 purple; 224 white 3.15:1 • 4. Inflated X pinched pods All inflated 882 inflated; 299 pinched 2.95:1 • 5. Green X yellow pods All green 428 green; 152 yellow 2.82:1 • 6. Axial X terminal flowers All axial 651 axial; 207 terminal 3.14: 1 • 7. Long X short stems All long 787 long; 277 short 2.84: 1 What happens if two character traits are followed simultaneously?

13. Fig. 13.16

15. Mendel’s Second Law Second Law=The Law of Independent Assortment: During the formation of gametes, the segregation of alleles at one locus is independent of that of the segregation of alleles at any other.

16. Genes’ eye view of meiosis and mitosis

17. Mendel’s First Law Each trait is governed by 2 particles*, one inherited from each parent. These two particles do not influence each other in any way within an individual, but separate, uncontaminated in any way, into gametes at the time of reproductive cell Formation. (an unstated corollary is that any pollen cell can fertilize any egg cell = random fertilization). Each trait is governed by 2 particles*, one inherited from each parent. These two particles do not influence each other in any way within an individual, but separate, uncontaminated in any way, into gametes at the time of reproductive cell Formation. (an unstated corollary is that any pollen cell can fertilize any egg cell = random fertilization). Mendel’s Second Law The Law of Independent Assortment: During the formation of gametes, the segregation of alleles at one locus is independent of that of the segregation of alleles at any other. A Gene's (allele) Eye View of Mitosis and Meiosis

18. Figure 10.5 Meiosis Accounts for the Segregation of Alleles (Part 1)

19. Figure 10.5 Meiosis Accounts for the Segregation of Alleles (Part 2)

20. Figure 10.8 Meiosis Accounts for Independent Assortment of Alleles

21. a A a A a A mitotic metaphase anaphase, telophase, cytokinesis a A a A

22. B A b a genotype: Aa; Bb replication A B Meiosis I metaphase A B a b a b Meiosis I anaphase, telophase, cytokinesis Meiosis I product cells A B A B a b a b

23. Meiosis I product cells A B A B Meiosis II metaphase a b a b Meiosis II metaphase Meiosis II anaphase, telophase, cytokinesis Meiosis II product cells AB A B AB A B ab a b ab a b

24. Meiosis I product cells A b A b Meiosis II metaphase a B B a Meiosis II metaphase Meiosis II anaphase, telophase, cytokinesis Meiosis II products cells Ab A b Ab b A aB a B aB a B

25. Eye Color Is a Sex-Linked Trait in Drosophila

28. Probability – Predicting Results Rule of addition: the probability of 2 mutually exclusive events occurring simultaneously is the sum of their individual probabilities. When crossing Pp x Pp, the probability of producing Pp offspring is probability of obtaining Pp (1/4), PLUS probability of obtaining pP (1/4) ¼ + ¼ = ½

29. Probability – Predicting Results Rule of multiplication: the probability of 2 independent events occurring simultaneously is the PRODUCT of their individual probabilities. When crossing Rr Yy x RrYy, the probability of obtaining rr yy offspring is: probability of obtaiing rr = ¼ probability of obtaining yy = ¼ probability of rr yy = ¼ x ¼ =1/16

30. Testcross Testcross: a cross used to determine the genotype of an individual with dominant phenotype -cross the individual with unknown genotype (e.g. P_) with a homozygous recessive (pp) -the phenotypic ratios among offspring are different, depending on the genotype of the unknown parent

33. Genes Phenotypes Genes pleiotropy polygenic inheritance

35. Figure 10.12 Inheritance of Coat Color in Rabbits “continuous” variation: multiple alleles of one gene

36. Gene Interaction (alleles of same gene) - dominance - incomplete dominance - co-dominance - lethal alleles Gene Interaction (alleles of different genes): - in different pathways (Drosophila eye pigmentation) - in same pathway - recessive epistasis

37. Fig. 13.18

38. codominance

40. Fig. 13.20

42. fly heads +/+ x Antp/+ Antennapedia mutant (Antp/+) ½ “Antp” (Antp/+) ½ “+” (+/+) wild-type (+/+) Antp/+ x Antp/+ 2/3 “Antp” (Antp/+) 1/3 “+” (+/+) ? ¼ +/+ (“+”) ½ Antp/+ (“Antp”) ¼ Antp/Antp (lethal)

43. Fig. 13.19

44. Extensions to Mendel

45. Eye Color Is a Sex-Linked Trait in Drosophila

46. w m+ w+ m white-eyed, normal-winged males wild type females w m+ w m+ x w+ m w m+ w+ m white-eyed, normal-winged female x red-eyed, miniature winged male (wild type) w m+ for male progeny, EXPECT: ½ white-eyed, normal-winged ½ red-eyed, miniature winged 64% of males fell into above classes, but 36% were either wild type Or doubly mutant !!!!!!!

47. white-eyed, normal-winged males w m+ x genetic recombination = chromosomal crossing over 36% of chromosomes in meiosis I: wild type females w m+ w+ m 36% of males are either doubly mutant or wild type : w+ m+ w m

48. Chiasmata visible in Locusta migratoria spermatogenesis A synaptonemal complex