The Reproductive System: Part A - Next2Eden

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Meiosis• Gamete formation involves meiosis• Nuclear division in the gonads in which thenumber of chromosomes is halved (from 2nto n)• Two consecutive cell divisions (meiosis Iand II) following one round of DNA replication• Produces four daughter cells• Introduces genetic variationCopyright © 2010 Pearson Education, Inc.
CentriolepairsInterphase cell2n = 4NuclearenvelopeChromatinInterphase eventsAs in mitosis, meiosis is precededby DNA replication and otherpreparations for cell division.MEIOSIS ICrossoverSpindleSisterchromatidsNuclear envelopefragments latein prophase ICentromereProphase IProphase events occur, as in mitosis. Additionally,synapsis occurs: Homologous chromosomes cometogether along their length to form tetrads. Duringsynapsis, the “arms” of homologous chromatids wraparound each other, forming several crossovers. Thenonsister chromatids trade segments at points ofcrossover. Crossover is followed through the diagramsbelow.Metaphase IThe tetrads align randomly on the spindleequator in preparation for anaphase.TetradDyadChromosomesuncoilNuclearenvelopesre-formCleavagefurrowAnaphase IUnlike anaphase of mitosis, the centromeres do notseparate during anaphase I of meiosis, so the sisterchromatids (dyads) remain firmly attached. However, thehomologous chromosomes do separate from each otherand the dyads move toward opposite poles of the cell.Telophase IThe nuclear membranes re-form around thechromosomal masses, the spindle breaks down, andthe chromatin reappears as telophase and cytokinesisare completed. The 2 daughter cells (now haploid)enter a second interphase-like period, calledinterkinesis, before meiosis II occurs. There is nosecond replication of DNA before meiosis II.Copyright © 2010 Pearson Education, Inc. Figure 27.6 (1 of 2)
Page 1 and 2: PowerPoint ® Lecture Slidesprepare
Page 3 and 4: Reproductive System• Sex hormones
Page 6 and 7: PeritoneumSeminalvesicleAmpulla ofd
Page 8 and 9: The Scrotum• Temperature is kept
Page 10 and 11: The Testes• Sperm are conveyed th
Page 12 and 13: Blood vesselsand nervesSpermatic co
Page 14: Seminiferoustubule(c)Interstitial c
Page 17 and 18: The Penis• External anatomy inclu
Page 19 and 20: The Male Duct System• Epididymis
Page 21 and 22: Blood vesselsand nervesSpermatic co
Page 24 and 25: UreterAmpulla of ductus deferensUri
Page 26 and 27: Accessory Glands: Prostate• Encir
Page 28 and 29: UreterAmpulla of ductus deferensUri
Page 30 and 31: Semen• Alkalinity neutralizes the
Page 32 and 33: Male Sexual Response• Erection:
Page 34 and 35: Copyright © 2010 Pearson Education
Page 38 and 39: MEIOSIS IIProphase IIMetaphase IIMe
Page 40 and 41: Number ofdivisionsSynapsis ofhomolo
Page 42 and 43: Copyright © 2010 Pearson Education
Page 44 and 45: Mitosis of Spermatogonia• Begins
Page 46 and 47: Meiosis: Spermatocytes to Spermatid
Page 48 and 49: Spermiogenesis: Spermatids to Sperm
Page 50 and 51: Approximately 24 daysGolgiapparatus
Page 52 and 53: Role of Sustentacular Cells• Tigh
Page 54 and 55: Role of Sustentacular Cells• Tigh
Page 56 and 57: HPG Axis1. Hypothalamus releases go
Page 58 and 59: 1Anteriorpituitary82GnRHVia portalb
Page 60 and 61: Mechanism and Effects of Testostero

The Reproductive System: Part A - Next2Eden

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