Biology 2250 rinciples of Genetics nnouncements B2250 edings nd roblems Lb 3 Informtion: B2250 (Innes) webpge downlod nd print before lb. Virtul fly: log in nd prctice http://biologylb.wlonline.com/ Ch. 4 p. 100 112 rob: 10, 11, 12, 18, 19 Ch. 5 p. 118 129 rob: 1 3, 5, 6, 7, 8, 9 Ch. 6 p. 148 165 rob: 1, 2, 3, 10 Weekly Online Quizzes Weekly Online Quizzes esults Mrks Oct. 14 - Oct. 25 Exmple Quiz Oct. 21- Oct. 25 Quiz 1 2 Oct. 28 Quiz 2 2 Nov. 4 Quiz 3 2 Nov. 10 Quiz 4 2 2** for logging in Exmple quiz: Quiz 1: nswers: http://webct.mun.c:8900/ Topics: Mendelin Genetics -Trnsmission of DN during cell division Mitosis nd Meiosis - Segregtion - Sex linkge (problem: how to get white-eyed femle ) - Inheritnce nd probbility - Independent ssortment - Mendelin genetics in humns - Linkge - Gene mpping - Tetrd nlysis (mpping in fungi) - Extensions to Mendelin Genetics - Gene muttion - Chromosome muttion - Quntittive nd popultion genetics Mendelin Inheritnce Determining mode of inheritnce: - single gene or more complicted - recessive or dominnt - sex linked or utosoml - probbility pproch: cross prents observed progeny compre with expected 1
Mendelin Genetics in Humns Determining mode of inheritnce roblems: 1. long genertion time 2. cn not control mting lterntive: * informtion from mtings tht hve lredy occurred edigree edigree nlysis: Humn edigrees trce inheritnce of disese or condition provide clues for mode of inheritnce (dominnt vs. recessive) (utosoml vs. sex linked) however, some pedigrees mbiguous determine probbility Mendel s Second Lw Independent ssortment: during gmete formtion, the segregtion of one gene pir is independent of other gene pirs. Genes independent becuse they re on different chromosomes Independent ssortment F 1 b b F 2 4 phenotypes 9 -B- 3 -bb 3 B- 1 bb Genotypes B b B b bb, bb Bb, BB Independent ssortment Test Cross Independent ssortment b bb gmetes b 1/4 b 1/4 b bb 1/4 B Bb 1/4 b bb 4 phenotypes 4 genotypes Fig 6-6 Interchromosoml ecombintion Inferred F 1 gmete types b b B 2
(Genes) Meiosis I Correltion of genes nd Chromosomes during meiosis Linkge of Genes - Mny more genes thn chromosomes 4 gmete types B b O b B - Some genes must be linked on the sme chromosome; therefore not independent Complete Linkge ecombinnt Gmetes? B b F 1 B b b F 1 gmetes B b b b dihybrid prentl Crossing over: - exchnge between homologous chromosomes Crossing over in meiosis I Crossing over in meiosis I (nimtion) Meiosis I - homologous chromosomes pir - reciprocl exchnge between non-sister chromtids Ch 4 meiosis nimtion: http://www. whfreemn.com/mg/ 3
Gmete Types F 1 B b b gmetes B rentl b b rentl b b ecomb. B B ecomb. Two Wys to produce dihybrid 1 B x bb b Note: B b B b 2 bb x BB b b b B B Chromtids omitted 1. Wys to produce dihybrid Cis B b B b B b b (dihybrid ) Gmetes: b b B Note: Chromtids omitted 2. Wys to produce dihybrid b B b B b b trns (dihybrid ) B Gmetes: b B b Two wys to produce dihybrid B b b B B b b B cis B b b trns b (dihybrid ) B Gmetes: b b B b B b Independent ssortment Fig 6-6 Interchromosoml Fig 6-11 Linkge Intrchromosoml 4
Exmple Exmple (cont.) Test Cross b bb How to distinguish: rentl high freq. ecombinnt low freq. b Exp. Obs. b 25 10 b bb 25 40 B Bb 25 40 b bb 25 10 100 100 Gmetes: b B b Therefore dihybrid: b (trns) B Linkge Mps Genes close together on sme chromosome: - smller chnce of crossovers between them - fewer recombinnts Therefore: percentge recombintion cn be used to generte linkge mp Linkge mps B lrge # of recomb. b C D smll number of recombinnts c d lfred Sturtevnt (1913) Testcross progeny: Linkge mps exmple b 2146 bb 43 Bb 22 bb 2302 Totl 4513 65 4513 = 1.4 % F 1.4 mu B 1.4 mp units dditivity of mp distnces seprte mps B C 7 2 combine mps C B 2 7 or Locus C B (pl. loci) 2 5 5
Linkge Linkge mps Devitions from independent ssortment Dihybrid gmetes 2 prent (noncrossover) common 2 recombinnt (crossover) rre % recombinnts function of distnce between genes % F = mp distnce Tomto Drosophil Linkge group = chromosome Summry Mendelin Genetics: Monohybrid cross (segregtion): - rtios (3:1, 1:2:1, 1:1) - dominnce, recessive - utosoml, sex-linked - probbility - pedigrees Dihybrid Cross (Indep. ssort.): - rtios (9:3:3:1, 1:1:1:1) - linkge (devition from I..) - recombintion - linkge mps 6