GN 301 Module 2: Mitosis and Meiosis

Purpose of mitosis

to replicate identical cells for different functions in the body

Define somatic cell:

a cell that does not produce gametes

List stages of mitosis

Prophase, Metaphase, Anaphase, Telophase

Prophase:

The chromosomes shorten and thicken. (60% of time)

Metaphase:

Chromosomes line up in the middle of the cell. (5% of time)

Anaphase: 

Chromatids break apart at the centromere and move to opposite poles. (5% of time)

Telophase:

Two nuclei formed after nuclear envelopes reform around each group of chromosomes. (30% of time)

Define Cytokinesis

the cytoplasmic division of a cell at the end of mitosis, bringing about the separation into two daughter cells.

Define meiosis

Cell division in a diploid cell that leads to gamete formation.

Reductional division:

The number of chromosomes in daughter cells gets cut in half from the original number.

Equational division:

The chromosome number is the same at the end as it was at the beginning.

Define crossing over and describe its importance:

Crossing over is recombination in Prophase I. 2 chromosomes come together and break apart when they overlap and switch some of their alleles. This allows variation from generation to generation as alleles switch around.

Biological Significance of meiosis

Constant Number of chromosomes and Provides variation from generation to generation

Constant Number of chromosomes

Since meiosis creates cells that become gametes, it’s important that the chromosome number is reduced to the original size because it would not be good if there were twice the number of original chromosomes.

Provides variation from generation to generation (2 ways)

1. crossing over: shuffling chromosomes between parents

2\.  independent assortment: genes independently separate themselves from one another when reproductive cells develop

Meiosis

is vital for fertilization

Mitosis

is vital for cell replication for different tasks in the body.

Meiosis

maintains a constant number of chromosomes.

Mitosis

does not pair chromosomes and so it ends up producing twice the original amount of cells.

Meiosis

provides variation from generation to generation.

Mitosis

replicates the exact same cell without any variation.

Meiosis

shuffles chromosomes between parents (there are 2^23 possible combinations of chromosomes).

Mitosis

creates the same mitotic problems each time.