Unit 4 – Lecture 2. Discuss Review the stages of Mitosis [cell cycle] with your partner. Mitosis...
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Transcript of Unit 4 – Lecture 2. Discuss Review the stages of Mitosis [cell cycle] with your partner. Mitosis...
DiscussReview the stages of Mitosis [cell cycle]
with your partner.
Mitosis – cell division in somatic [body] cells[I]PMAT
[interphase]prophasemetaphaseanaphasetelophase
MeiosisMeiosis – cell division to create gametes
sex cells / reproductive cells / egg&spermMeiosis I –
IPMATMeiosis II –
PMAT
Meiosis IMeiosis I – similar to mitosis [diff in red]
[interphase…]Prophase I
chromosomes condensenuclear envelope disappearshomologous chromosomes pair
instead of chromatidscrossing over occurs
Crossing OverCrossing over – exchange of genetic
information between homologous chromosomescontributes to genetic diversity of resulting
gameteshomologous chromosome pair = tetrad
tetra = four not required:
chiasma(ta) – place at which crossing over occurs
Meiosis I – cont’d[Meiosis I]
Metaphase Ispindle fibers move tetrads to cell equator
[similar to metaphase plate / equatorial plate in mitosis]
Meiosis I – cont’d[Meiosis I]
Anaphase Ihomologous chromosomes are each
pulled by spindle fibers to cell poles
Meiosis I – cont’d [Meiosis I]
Telophase Ihomologous chromosomes each
arrive at cell polesnuclear envelopes reformspindle fibers break downcytoplasm divides [cytokinesis]
Meiosis I – cont’dMeiosis I: End Result –
2 diploid cells with:same amount of informationdifferent combination of information
Discuss
What processes happen during interphase?
If there is no interphase, what processes are NOT going to happen in between the first stages of meiosis and the second meiosis?
Meiosis II – cont’d[Meiosis II]
Anaphase IIchromosomes pulled apart at
centromeres; [form chromatids]
chromosomes [chromatids] pull toward poles
Meiosis II – cont’d[Meiosis II]
Telophase II – nuclear envelopes reformspindle fibers break downcytokinesis
Meiosis II – cont’dMeiosis II: End Result –
4 haploid cells with:half of info as original cell different combination of information
Meiosis – cont’dCells produced from meiosis are genetically
differentdue to:
crossing over [in prophase I]independent assortment [in metaphase I]
random distribution of homologues in metaphase I