Question

What are the stages of Meiosis I and Meiosis II in order as the happen.

Answer 1

Meiosis I:

Prophase I - Homologus chromosomes pair up (synapsis) and form a tetrad. Sometimes non-sister chromatids exchange genetic information during the process of crossing over.

Metaphase I- Tetrads line up at the center of the cell.

Anaphase I - Homologous pairs are split up.

Telophase I/Cytokinesis - Two daugher cells form that have half the chromosome number of the parent cell but each chromosome consists of a pair of sister chromatids.

Interkinesis - break period

Meiosis II:

Prophase II - A new spindle forms

Metaphase II- Each chromosome lines up at the middle of the cell.

Anaphase II - The sister chromatids are separated and move to opposite ends of the cell.

Telophase II - Two new nuclei are formed in each cell. Each nucleus contains a haplod (n) number of chromosomes.

Cytokinesis- End result of meiosis is 4 haploid daughter cells

Answer 2

Prophase I

DNA replication precedes the start of meiosis I. During prophase I, homologous chromosomes pair and form synapses, a step unique to meiosis. The paired chromosomes are called bivalents, and the formation of chiasmata caused by genetic recombination becomes apparent. Chromosomal condensation allows these to be viewed in the microscope. Note that the bivalent has two chromosomes and four chromatids, with one chromosome coming from each parent.Prometaphase I

The nuclear membrane disappears. One kinetochore forms per chromosome rather than one per chromatid, and the chromosomes attached to spindle fibers begin to move.Metaphase I

Bivalents, each composed of two chromosomes (four chromatids) align at the metaphase plate. The orientation is random, with either parental homologue on a side. This means that there is a 50-50 chance for the daughter cells to get either the mother's or father's homologue for each chromosome.Anaphase I

Chiasmata separate. Chromosomes, each with two chromatids, move to separate poles. Each of the daughter cells is now haploid (23 chromosomes), but each chromosome has two chromatids.Telophase I

Nuclear envelopes may reform, or the cell may quickly start meiosis II.Cytokinesis

Analogous to mitosis where two complete daughter cells form.