MITOSIS AND MEIOSIS CHAPTER SUMMARY QUESTIONS. Hyde Chapter 3 Solutions See table 3.1 for a summary answer.

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1 Hye hpter 3 Solutions 9 3 MITOSIS N MEIOSIS HPTER SUMMRY QUESTIONS 2. See tle 3.1 for summry nswer. 4. When eukryoti hromosome replites uring the S phse of the ell yle, one hromosome eomes two hromtis, tthe ner the entromere. These re sister hromtis. hromtis of ifferent hromosomes re nonsister hromtis. 6. The terms reutionl n equtionl refer to the segregtion of hromosomes uring meiosis. The first ivision is terme reutionl euse the homologous hromosomes seprte from eh other, reuing the numer of hromosomes in hlf. The seon meioti ivision is lle equtionl euse the numer of hromosomes remins the sme lthough the numer of hromtis is hlve. 8. fter the S phse, the sister hromtis re kept together y multiprotein omplex terme ohesin. The nphse-promoting omplex (P) triggers the estrution of ohesin. tivte P tlyzes the uiquintion n egrtion of the protein seurin, n inhiitory protein tht ins n intivtes protese lle seprse. Free from seurin, seprse n now egre ohesin n permit the seprtion of the sister hromtis from eh other. 10. The two meioti mehnisms tht generte geneti iversity re (1) n inepenent ssortment of hromosomes, whih strts in metphse I n ens in nphse I; n (2) rossing over etween nonsister hromtis of homologous hromosomes, whih tkes ple in prophse I. 12. In iploi orgnisms, hromosomes our in pirs. The hploi numer, or numer of pirs of hromosomes, my e even (4 in the fruit fly, for exmple) or o (23 in humns). However, the totl iploi numer is given y 2 the numer of hromosome pirs, n therefore it will e n even numer In spermtogenesis, oth meioti ivisions re followe y equl ytoplsmi ivisions, yieling four funtionl gmetes. In oogenesis, unequl ytoplsmi ivisions usully proue only one funtionl gmete n up to three polr oies.

2 10 Hye hpter 3 Solutions 2. One spermtogenesis egins, it ours ontinuously. Oogenesis, on the other hn, strts uring emryoni evelopment n then puses until puerty, where it resumes for only one ooyte, usully, per month. 3. Spermtogenesis ours throughout ult life, while oogenesis ens t menopuse. 4. Spermtogenesis results in the proution of hunres of millions of sperm per y, wheres on verge humn femle proues out 400 ov in her lifetime. EXERISES N PROLEMS Mitosis, prophse, 2n = 6 (the two prllel thres represent sister hromtis); or meiosis II, erly prophse, 2n = 12 (eh thre represents hromosome, n sister hromtis re not evient yet). Mitosis, metphse, 2n = 6, or meiosis II, metphse, 2n = 12. Mitosis, nphse, 2n = 6, or meiosis II, nphse, 2n = 12. Meiosis I, erly prophse, 2n = 6 (eh thre represents hromosome, n sister hromtis re not evient yet) e. Meiosis I, nphse, 2n = 6 f. Meiosis II, nphse, 2n = n ivlent (= ys) (= Tetrs) Humn eing Gren pe 14 7 Fruit fly 8 4 House mouse 40 20

3 Hye hpter 3 Solutions 11 Rounworm 2 1 Pigeon o onstritor riket Lily Inin fern The numer of omintions is 2 n where n = the numer of ifferent hromosome pirs. In this se, n = 6, so we expet 2 6 = 64 ifferent omintions. 24. N (Numer of hromtis) Ploiy Spermtogonium or oogonium 2 2n Primry spermtoyte or primry ooyte 4 2n Seonry spermtoyte or seonry ooyte 2 n Spermti or ovum 1 n Sperm 1 n 26.. The primry ooyte is iploi n will unergo meiosis, ut only one funtionl ovum results from eh primry ooyte: 1 50 = 50 eggs.. Eh seonry ooyte will unergo meiosis II to proue n ovum n polr oy: 1 50 = 50 eggs. 28. Homologous hromosomes will pir uring meiosis. Eh gmete gets one of eh hromosome,,,,, n E. Fertiliztion fuses two ells with the hromosome omplement given. Sine root ells re somti tissue, these ells will e iploi. Therefore, the nswer is. EE hromosomes (n). 42 hromosomes (2n). 63 hromosomes (3n) 32. The sperm ells proue y the pollen prent hve the genotype. The femle prent ontins the egg ell n two polr nulei, ll of whih hve genotype. One sperm ell will fertilize the egg ell resulting in iploi zygote with genotype. The two polr nulei re fertilize y seon sperm ell, prouing triploi enosperm with genotype. 34. The numer of ifferent gmetes proue y eh prent is Using the n rule (refer k to hpter 2), we n lulte the numer of ifferent types of offspring tht n e proue from the mting: = 2 40 possiilities! 36. queen rone yiels for sons (or gmetes):,,, n for ughters:,,,.

4 12 Hye hpter 3 Solutions or out = 4 The numer of gmetes proue is 2 n, where n = numer of inepenently ehving entities. If the genes re ompletely inepenent, we expet 2 50, n if they re ompletely linke, then the numer of ifferent gmetes will e etermine y the numer of ifferent hromosomes, so we expet 2 2. In relity, the numer flls etween these two extremes. 40. Mitosis Meiosis I Meiosis II Mitosis Meiosis I Meiosis II hromosome no hromti no Piogrms N HPTER INTEGRTION PROLEM. The proess of mitosis oes not relte iretly to Menel s rules. The ehvior of hromosomes uring meiosis, however, explins oth equl segregtion (first lw) n inepenent ssortment (seon lw). Menel s lw of segregtion n e expline y the homologous piring n segregtion of hromosomes uring meiosis. Only one hromosome from eh homologous pir goes into gmete. So, for exmple, the n lleles will eh segregte to ifferent gmete. This is lso true for the /, /, n / lleles. Menel s lw of inepenent ssortment n e expline y the reltive ehvior of ifferent (nonhomologous) hromosomes uring meiosis I. The piring rrngement, seprtion, n migrtion of one homologous pir o not influene the orienttion of n jent homologous pir. In our exmple, the ssortment of gene is inepenent of tht of genes,, or. In other wors, gmete is eqully likely to inherit the n lleles or the n

5 Hye hpter 3 Solutions 13 lleles. Similrly, it n otin the n lleles or the n lleles, with equl proilities.. Gene is foun on the p rm of n roentri hromosome, while genes n re foun on the q rm of ifferent metentri hromosomes.. The ell is in prophse of mitosis. The hromosomes re onense ut not yet line up in the enter of the ell. In prophse I of meiosis there woul e synpsis etween mternl n pternl homologs. In prophse II of meiosis there woul only e four hromosomes (the hploi numer) in the ell... e. Four tetrs will form uring prophse I of meiosis. These n lign in eight ifferent wys in metphse I. To rw them ll, keep one tetr fixe n hnge the other three tetrs in systemti fshion. The following eight possile rrngements orrespon to Menel s seon lw of inepenent ssortment. Eh of these rrngements will our with equl proility n eh will proue two ifferent types of gmetes.

6 14 Hye hpter 3 Solutions f. The numer of hromosoml omintions is 2 n, where n = the numer of ifferent hromosome pirs. Thus, there re 2 4 = 16 possile omintions. The hne of getting one memer of set is 1/2; so the hne of getting, or ll four from the mternl sie, is (1/2) 4 = 1/16. g. To solve this prt use n empiril pproh tht lists ll possile omintions with two hromosomes from one prent. These re,,,,, n. So the nswer is 6/16 = 3/8. h. The set of gmetes with mixture of mternl n pternl hromosomes onsists of ll gmetes exept those with only mternl or only pternl hromosomes. The hne of gmete getting only mternl hromosomes is 1/16 (see prt f). Similrly, the hne of gmete getting only pternl hromosomes will e 1/16. Therefore, the hne of getting mixture of mternl n pternl hromosomes is 1 (1/16 + 1/16) = 14/16 = 7/8.