Reducing the Chromosome Number (Meiosis) - QUIZ 2

What is meiosis's function?

Reduces the chromosome number and introduces genetic variation.

What do you start and end with during this process?

Start: 1 diploid cell(2n).

End: 4 haploid (n) daugther cells.

What happens during Prophase I?

Synapsis of homologous chromosomes, crossing over occurs. Nuclear membrane breaks down.

What happens during Metaphase I?

Homologous pairs align at equator; independent assortment determines orientation.

What happens during Anaphase I?

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

What happens during Telophase I?

Nuclear envelope may reform; cytokinesis may occur → (THE RESULT OF THIS PROCESS) 2 haploid cells (n).

What happens during Interkenesis?

Short resting period during the cycle, no DNA replication occurs

Meiosis II consists of.....

- Prophase II

- Metaphase II

- Anaphase II

- Telophase II

In Prophase II...

Cells have one chromosome from each homologous pair.

In Metaphase II....

Chromosomes align at equator.

In Anaphase II.....

Centromeres split; sister chromatids separate and move to poles.

Telophase II

Nuclear membranes reform, chromosomes return to chromatin.

Crossing over

Prophase I, homologues exchange segments, exchange of nonsister chromatids.

Independent assortment

Metaphase I, random orientation of homologues.

Fertilization

Restores diploid number (n + n = 2n).

Meiosis

Divisions: 2; Cells produced: 4 haploid, genetically variable; When it occurs: special occasions (gamete formation); Crossing over: Occurs in Meiosis I only, reductive division.

Mitosis

Divisions: 1; Cells produced: 2 diploid, genetically identical; When it occurs: continual growth and repair, Just like Meiosis II.