Lectue Outline 10/26/05 Consequences of meiosis Gmetes e geneticlly vile Inepenent ssotment Cossing ove Lots of pctice polems Eos in meiosis Why epouce sexully? Mitosis vs meiosis: Mitosis ensues exct epliction of the pent cell Meiosis pouces vile, hploi, gmetes. Gmetes e not ienticl, ecuse of: Inepenent ssotment Cossing ove Inepenent ssotment Key Mtenl set of Ptenl set of Possiility 1 Possiility 2 Fo ech pi of, mtenl n ptenl homologues e sote into ughte cells inepenently of the othe pis Two eqully pole ngements of t metphse I Metphse II ughte cells Figue 13.10 Comintion 1 Comintion 2 Comintion 3 Comintion 4 1
Consequences fo genetic vition Consequences fo genetic vition Lel two lleles of gene n e vs white fethes nothe gene on iffeent chomosome: n e vs non-e fethes This iniviul inheite with lleles fo e fethes n non-e fethes its fthe White fethes n e fethes fom its mothe Wht kins of gmetes will it pouce though inepenent ssotment? Cossing Ove Pouces ecominnt tht cy genes eive fom two iffeent pents Pophse I of meiosis Metphse I Tet Nonsiste chomtis Chism, site of cossing ove The loction of cossoves is nom This tet hs 3 cossoves: 2&3 1&3 2&4 Metphse II Figue 13.11 ughte cells ecominnt Cn occu etween ny pi of chomtis 2
Spinle fies fom one pole ttch to OTH siste chomtis Cossoves e essentil fo coect lignment t metphse 1 Spinle fies fom the othe pole ttch to the othe homolog Chismt hol the pi togethe while Tug of w ligns tets Cossoves e nom If two genes e close togethe on the chomosome, they e likely to e inheite togethe. Consequences fo genetic vition Test youself: e vs white fethes own vs white eggs ssume the iniviul is iploi with 3 pis of Is this mitosis o meiosis? Why? Wht stge? Wht kins of gmetes cn it pouce? 3
4 Wht is wong with this pictue? gin, ssume the iniviul is iploi with 3 pis of Wht is wong with this pictue? Moe pctice Mitosis o meiosis? Is it coect? Mitosis o meiosis? Is it coect? Even moe pctice
Polyploiy Eos in meiosis uplictions of entie genomes Seen in mny plnt species Consequences fo epouctive isoltion x --> How oes meiosis wok in tht tiploi? Steile neuploiy uplictions o eletions of single Eos in meiosis Eos in meiosis: neuploiy Most humn neuplois e ftl. Exception: tisomy 21 (owns Synome) Exception: XXY Tune s synome mles Ntul vition in chomosome nume Species iffe getly in chomosome nume: E. coli: 1 cicul chomosome osophil melnogste: 4 Woo fen: 2N=164 Chimps n goills hve 2N=48 Humns hve 2N=46 How woul tht ffect epouction in pehomini/pe-chimp ncestos? Imgine meiosis n the upliction/eletions tht woul e in the hyi zygotes How woul the hyi (2N=47) mke gmetes? How woul pi? 5
vntges of sex: Why sex? voi isese nns e popgte sexully Cvenish viety ccounts fo lmost ll of the commecil nns Pnm isese (Fusium wilt) is speing though si It s peecesso viety, the Gos Michel suffee simil fungl light tht wipe out tht cop in the 1950s isvntges: Nee to fin mte Only pss on hlf of you genes Tht new comintion of genes might e wose... vntges of sex: voi isese on t puchse the sme lottey ticket twice Puge muttions Tht s lot of nns... One solution: ee esistnt vieties Imgine tht two pentl vieties iffe in 15 single genes. To get the esie llele t ech locus, 0.515 = 1/30,000 http://www.popsci.com http://www.ug.eu/fuit/nn.htm 6
Some ognisms hve oth sexul n sexul stges vntges of sex Puge eleteious muttions Most of them e eleteious Muttions occu evey genetion Ove time, ech chomosome will ccumulte sevel eleteious muttions Without meiosis, the nume of muttions on chomosome will only incese -+++-+ ++-++- iffeent lineges will cquie iffeent muttions Cossing ove cn pouce some gmetes with fewe muttions ++++- 7