Meiosis Unit 1 pt 2

Meiosis occurs in__________

sexually reproducing organisms

Function of Meiosis?

reduces chromosome number (diploid → haploid) and introduces genetic variation.

how many cell at the start of meiosis

1 diploid cell

how many cell of the end of meiosis

4 haploid daughter cells.

meiosis is also called…..

reducing devision

meiois phases

Prophose, Metaphase, Anaphase, Telophase(PMAT)

What happens in Prophase 1

• Synapsis of homologous chromosomes

• , crossing over occurs.

• Nuclear membrane breaks down.

What happens in Metaphase 1

• Homologous pairs align at equator;

• independent assortment determines orientation.

What happens in Anaphase 1

Homologues (still with 2 chromatids) separate, pulled by spindle fibers.

What happens in Telophase 1

• Nuclear envelope may reform;

• cytokinesis may occur → 2 haploid cells (n).

Interkinesis

• Short rest period between divisions.

• No DNA replication occurs. Chromosomes still have two chromatids.

Meiosis 2 is also called…..

Equational Division

What happens in Prophase II

Cells have one chromosome from each homologous pair.

What happens in Metaphase II

Chromosomes align at equator.

Anaphase II

Centromeres split; sister chromatids separate and move to poles.

Telophase II

Nuclear membranes form; cytokinesis produces 4 haploid daughter cells.

In Genetic Variation, what happens in crossing over?

Prophase I, homologues exchange segments.

In genetic variation, what happens in independent assortment

Metaphase I, random orientation of homologues.

in genetic variation, fertilization…

Fertilization restores diploid number (n + n = 2n).

Meiosis has how many divisions

2

Mitosis has how many divisions

1

Meiosis has how many cells produced

4 haploid, genetically variable

How many cells produced in Mitosis

2 diploid, genetically identical.

When does meiosis occur?

special occasions (gamete formation)

When does mitosis occur

continual growth and repair.

Crossing over occurs in what process only

Meiosis 1