Chapter 11.4 Meiosis 2012 notes.pdf
Chapter 11.4 Meiosis 2012 notes.pdf
Chapter 11.4 Meiosis 2012 notes.pdf
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1. Chromosome #<br />
<br />
W/2 parents inherit single copy of gene from each parent<br />
Org. produces gametes (sex cells)—those 2 sets of genes sep.<br />
(each gamete = 1 set of genes)<br />
A. Diploid Cells<br />
Homologous: parental set of chromosomes<br />
Ex: Humans = 46 total chrom, 23 from dad, 23 corresponding chrom<br />
from mom<br />
Diploid (2N): “2 sets”; cell (body) w/both parent sets<br />
B. Haploid Cells<br />
Single sets of chromosomes<br />
Haploid (1N): cell (gametes) w/1 set
2. Phases of <strong>Meiosis</strong><br />
<br />
# of chrom/cell cut in half: haploid<br />
Process of reduction division (1 rep/2 div—<strong>Meiosis</strong> I & <strong>Meiosis</strong><br />
II)<br />
Homologous chrom separate<br />
A. <strong>Meiosis</strong> I<br />
Interphase—b/4 <strong>Meiosis</strong> I, cell grows & copies chrom (similar to<br />
mitosis)
Prophase I<br />
<br />
Chrom pair w/homologous chrom<br />
Homologous chrom form tetrad = contains 4 chromatids<br />
Crossing Over occurs: exchange of alleles;<br />
new combos formed = genetic diversity
Metaphase I—M is for middle<br />
<br />
Paired homologous chromosomes line up in middle of cell<br />
Anaphase I—A is for apart<br />
Spindle fibers pull hom. chromosomes apart
Telophase I & Cytokinesis<br />
<br />
Nuclear envelope forms around ea. cluster of chrom<br />
2 new cells; gen different cells<br />
<strong>Meiosis</strong> I Overview:
<strong>Meiosis</strong> II<br />
<br />
2 nd division; no chrom replication<br />
Prophase II<br />
Chrom visible (ea. Consisting of 2 chromatids)<br />
Metaphase II, Anaphase II, Telophase II, & Cytokinesis<br />
Sim to <strong>Meiosis</strong> I<br />
EXCEPTION: end with 4 Haploid Daughter Cells
Gametes to Zygotes<br />
<br />
Haploid cells = gametes (sex cells)<br />
4 sperm cells<br />
1 Egg, 3 polar bodies (not involved in reproduction)<br />
Zygote: fertilized egg; goes thru cell division—mitosis = new<br />
org formed
Phases of <strong>Meiosis</strong>
Comparing Mitosis vs. <strong>Meiosis</strong><br />
<br />
Mitosis<br />
<strong>Meiosis</strong><br />
2 identical cells 4 genetically<br />
different<br />
Diploid<br />
Haploid<br />
Body Cells<br />
Sex Cells<br />
1 Division 2 Divisions
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