Lab 22 Meiosis, spermatogenesis, oogenesis.pptx -...

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GAMETOGENESISSomatic body cellshave23 pairsof chromosomes(total of 46)Chromosome pair: 1 maternal chromosome, 1 paternalchromosomeHomologous chromosomesCarry genes for the same characteristicsSomatic cells arediploid,or2n
GAMETOGENESISGameteshave only 23unpairedchromosomesThey arehaploid, ornOnly carry genes from one parent
MEIOSIS COMPARED TO MITOSISMitosis generates identical daughter cellsMeiosisgenerates gametes - differs from mitosis2 consecutive cell divisions (meiosis I and II)Only 1 round of DNA replicationbeforemeiosis IProducesfour genetically unique daughter cells
MEIOSIS COMPARED TO MITOSISFunctions of meiosisNumber of chromosomes are cut in half (2nton)Introduces genetic diversity, as all daughter cells aregenetically different from original cell(and each other)Meiosis has the same basic phases as mitosis, butsince there are 2 divisions, they are named:Meiosis IMeiosis IIProphase IProphase IIMetaphase IMetaphase IIAnaphase IAnaphase IITelophase ITelophase II
Mother cell(before chromosome replication)ChromosomereplicationChromosomereplication2n=4ReplicatedChromosome(sisterchromatids)ProphaseMetaphaseMetaphase IProphase IMITOSISMEIOSISChromosomesalign at themetaphase plateSister chromatids separateduring anaphaseDaughtercells ofmitosis2n2nMeiosis IIDaughter cellsof Meiosis IHomologous chromosomesseparate but sister chromatidsremain together during anaphase ITetrads align randomlyat the metaphase plateTetrad formed bysynapsis ofreplicated homologouschromosomesNo further chromosomalreplication; sister chromatidsseparate during anaphase IIDaughter cells of meiosis II(usually gametes)nnnn
MEIOSISMeiosis IReduces chromosome number from 2nnDiploid to haploidProphase Ihas events not seen in mitosis or meiosis II
MEIOSISProphase ISynapsis:Homologous chromosomes pair up - formingtetradsconsisting of 2 sets of sister chromatidsCrossover:Exchange between paternal and maternal chromatidsResults in unique chromosomes that are mixtures ofmaternal and paternal genes
MEIOSISMetaphase ITetrads line up randomly at spindle equatorIndependent assortmentof maternal/paternalAnaphase IHomologous chromosomes are separatedSister chromatids stay together
INDEPENDENT ASSORTMENT – METAPHASE IX = maternalX = paternal
With 2 chromosomes, there are 4 possible combinationsWith 23 chromosome, there are 8,388,608INDEPENDENT ASSORTMENT – METAPHASE I
MEIOSIS COMPARED TO MITOSISMeiosis IAftermeiosisI, each daughter cell has:2 copies (sister chromatids) of one member of eachhomologous pair and none of the otherA haploid chromosomal numberStill-connected sister chromatids are considered onechromosome (even though there is twice the amount ofDNA in each chromosome)

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Term
Winter
Professor
erika campeau
Tags
Mitosis, meiosis II

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