Meiosis

Prophase I

• Nuclear membrane dissolves.

• Spindle fibers begin to form.

• DNA condenses into visible chromosomes.

• Homologous chromosomes pair up and MAY undergo crossing over.

• Centrioles move to opposite poles of the cell.

Metaphase I

• Spindle fibers attach to homologous chromosome pairs.

• Homologous chromosome pairs line up at the center of the cell.

Anaphase I

• Spindle fibers pull homologous chromosomes to opposite poles of the cell.

Telophase I

• Nuclear membrane reforms.

• Chromosomes may partially unwind into DNA.

• Cytokinesis I occurs, resulting in two haploid (1n) cells.

Prophase II

• Nuclear membrane dissolves.

• DNA condenses into visible chromosomes.

• Centrioles move to opposite poles of each cell.

• Spindle fibers begin to form.

Metaphase II

• Spindle fibers attach to the centromeres of individual chromosomes.

• Chromosomes (sister chromatids) line up at the center of each cell.

Telophase II

• Nuclear membrane reforms around each set of chromosomes.

• Chromosomes decondense into DNA.

• Cytokinesis II occurs, resulting in four genetically unique haploid (1n) cells.

Synapsis

Pairing of homologous chromosomes during Prophase I

Tetrad

Each pair of homologous chromosomes.

Crossover

Exchange of DNA between homologous chromosomes.

Genetic recombination

Result of crossover

Independent assortment

Random assortment of homologous pairs into daughter cells during Anaphase I.

Oogenesis

Production of mature egg cells (ova).

Polar bodies

Degenerate products of oogenesis.

Karyotype

Arrangement of chromosomes in an organism.

Pedigree

Family record showing trait inheritance over generations.

Genetic Screening

Process for identifying genetic disorders.

Diploid (2n):

Two sets of chromosomes.

Haploid (1n)

One set of chromosomes.

anaphase II

spindle fibers pull sister chromatids to opposite poles of the cell