Meiosis—The
Process that
Fosters Genetic
Diversityhttp://www.uic.edu/classes/bios/bios100/lecturesf04am/lect16.htm
Karyotype• A display of
condensed chromosomes arranged in pairs.
Meiosis• A type of cell division that reduces
the number of chromosomes from diploid to haploid.
• Meiosis creates genetic diversity through crossing over and independent assortment.
• Meiosis ONLY creates sex cells
Synapsis • During Prophase I, replicated
homologues pair up and become physically connected along their lengths by a zipper-like protein structure (the synaptonemal complex).
Crossing Over• The exchange of corresponding
segments of DNA molecules by non-sister chromatids.
Chiasma/Chiasmata (plural)• The point where crossing over has
occurred and the homologs are still associated due to cohesion between sister chromatids
Interphase• Chromosomes
replicate to form sister chromatids.
Prophase I• Crossing over
occurs during synapsis.
• Chiasma are evident
Metaphase I• Chromosomes
line up by homologous pairs on the metaphase plate
• Alignment is independent of maternal/paternal origin
Anaphase I• Each pair of
homologous chromosomes separates
Telophase I & Cytokinesis• Two haploid
cells form, each chromosome still consists of two chromatids
Prophase II• A new spindle apparatus forms
Metaphase II
Anaphase II
Telophase II & Cytokinesis• Four haploid, genetically unique cells
form.
Telophase I & Cytokinesis• Two haploid
cells form, each chromosome still consists of two chromatids
Telophase I & Cytokinesis• Two haploid
cells form, each chromosome still consists of two chromatids