Meiosis—The Process that Fosters Genetic Diversity

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