Meiosis

Meiosis

Type of cell division that results in four daughter cells each with 1/2 the # of chromosomes (n) of a diploid cell.

Haploid

Single set of unpaired chromosomes (n)

n

Abbreviation for haploid

2n

Abbreviation for diploid

Diploid

2 complete sets of chromosomes (2n)

Somatic cells

Regular body cells (2n)

Gamete cells

Sex cells (n)

Homologous chromosomes

Pair of chromosomes (one from each parent) with genes for the same characteristic; same size, centromere position.

3 ways homologous chromosomes are similar

Same type of genes

Same size & length

Same centromere position

Tetrad

Homologous chromosomes paired up with one another

Crossing over

Exchange of DNA between homologous chromosomes. Creates genetic variability in gamete cells.

Metaphase 1

Tetrads line up at the center of the cell.

Anaphase 1

Tetrads are pulled apart. Chromatids remain attached.

Prophase 1

Spindles form, centrioles move to poles, and nuclear envelope breaks down. Homologous chromosomes pair up with one another to form a tetrad and crossing over occurs.

Purpose of crossing over

To create genetic variability between gamete cells

Karyotype

Image of homologous chromosomes lined up in order; used to diagnose disorders, determine sex of baby, and determine # of chromosomes

46

Number of chromosomes in somatic cells (2n) of humans

23

Number of chromosomes in gamete cells (n) of humans

XX

Female sex chromosomes

XY

Male sex chromosomes

Prophase 2

Nuclear envelope breaks down and spindles begin to form. Centrioles move to the poles.

Metaphase 2

Chromosomes line up at the center of the cell. Spindles attached to the centromeres.

Anaphase 2

Chromatids are pulled apart.

Telophase 2

Nuclear envelope reforms, spindles begin to disappear and chromosomes start to uncoil

Cytokinesis 2

Division of cytoplasm and splitting of cells. 4 haploid daughter cells are produced.

Two

Number of divisions in meiosis

One

Number of divisions in mitosis

Similarities between mitosis and meiosis

Types of cell division

Create daughter cells

Go through interphase (G1, S, G2)

Go through PMAT (prophase, metaphase, anaphase, telophase)

Go through cytokinesis

Start as diploid (2n)

Differences between mitosis and meiosis

Meiosis has 2 divisions; Mitosis has 1 division

Meiosis makes haploids; Mitosis makes diploids

Meiosis makes 4 cells; Mitosis makes 2

Meiosis makes gametes; Mitosis makes somatic

Meiosis pair during metaphase; Mitosis do not pair during metaphase

Meiosis makes genetically different daughter cells; Mitosis makes identical daughter cells

Purpose of Meiosis

To make gamete cells (haploid) for sexual reproduction

Purpose of Mitosis

To make somatic cells to repair or replace cells or form growth