B SMART Meiosis It takes two baby 46

B SMART

Meiosis It takes two baby….

46 23 46 + haploid 23 haploid fertilization 46

But before we begin…. Homologous chromosomes: • 1 from each parent • carry genes that control the same inherited traits. karyotype

And remember. . Chromatin Chromatid Sister chromatid Chromosomes Sister chromatid Replicated homologous chromosomes

Interphase Prophase 1 Meiosis 1 Metaphase 1 Anaphase 1 Telophase 1 • chromosomes replicate • chromatin condenses • homolog. chrom. pair up • (note: ea. chrom. consists of 2 chromatids) • Nuclear envelope breaks down • Spindle fibers form • Homologous chromosomes line up at middle • Centromeres attach to spindle fibers • Homologous chromosomes move to opposite ends

Meiosis 2 Prophase 2 Metaphase 2 Cytokinesis Anaphase 2 • A haploid number of chromosomes line up at middle • Sister chromatids move to opp ends • nuclear membranes form • 4 unique haploid cells (n) Cytokinesis

Note. . Male gametes 4 haploid gametes … 4 sperm Female gametes 4 haploid gametes … 1 Ovum (egg) & 3 Polar Bodies

Also. . • Meiosis I • Prophase I – Crossing over: segments are exchanged between a pair of homologous chromosomes (swap genetic info)

• Ways Meiosis Provides Variation • Depending on how the chromosomes line up at middle, 4 gametes w/ 4 different combos of chromosomes can result. • crossing over • fertilization, when gametes randomly combine.

Meiosis

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