TEAS 7 Science: Mitosis and Meiosis

Mitosis

Division of the a cell's nucleus for growth and repair of the cell.

Outcome of Mitosis

Two genetically identical daughter cells

Steps of Mitosis

1. Interphase

2. Prophase

3. Metaphase

4. Anaphase

5. Telophase

Cytokinesis

The division of the cytoplasm to form two separate daughter cells. Occurs at end of telophase.

Interphase

Cell grows, performs its normal functions, and prepares for division.

Consists of G1, S, and G2 phases during which DNA replicates.

Prophase

Longest phase of mitosis, during which the chromosomes condense and become visible.

Centrioles separate and move to opposite sides of the nucleus.

Nuclear membrane disappears

Metaphase

Chromosomes line up in the middle of the cell

Metaphase = middle

Anaphase

Chomosomes move apart, from the center to the poles

Anaphase = apart

Telophase

Chromosomes move to opposite ends of the cell and two nuclei are formed. Nuclear membrane reappears. The new daughter cells separate via cytokinesis

Meiosis

Cell division that produces 4 gamete cells in sexually reproducing organisms, each with half the genetic information of the originating cell

Germ cell

Reproductive cell that produces ova (eggs) or sperm

Gamete

Sex cell that contains half the genetic information

Sperm or ovum (egg)

Steps of Meiosis I

Prophase I, Metaphase I, Anaphase I, Telophase I

Steps of Meiosis II

Prophase II, Metaphase II, Anaphase II, Telophase II

What happens at the end Interphase?

DNA replicates

Does Interphase happen before both mitosis and meiosis?

Yes.

Homologous chromosomes

Chromosomes that have the same sequence of genes, that have the same structure, and that pair during meiosis.

Crossing Over

Process in which homologous chromosomes exchange portions of their chromatids during meiosis.

Chromatid

One half of a duplicated chromosome

Prophase I

Homologous chromosomes pair up and form tetrads.

Crossing over occurs

Metaphase I

Paired homologous chromosomes line up in the center of the cell

Anaphase I

Homologous chromosomes separate toward opposite poles

Telophase I

Nuclear membrane forms and cytoplasm divides

2 daughter cells are formed

What is the end product of Meiosis I?

2 haploid cells

Sister chromatids have not separated (haploid set)

Prophase II

The first phase of meiosis II. Prophase II is identical to mitotic prophase, except that the number of chromosomes was reduced by half during meiosis I.

Metaphase II

Sister chromatids line up in the middle

Anaphase II

Sister chromatids separate to opposite poles

Telophase II

Nuclear membrane reforms and cytoplasm divides.

4 haploid daughter cells formed

Sister Chromatids

Joined copies of the original chromosome

Haploid

Cell having only one complete set of chromosomes. Sperm and ova are haploid cells.

Diploid

Cells with two complete sets of chromosomes, one from each parent.

How many chromosomes do human cells have?

46 (23 pairs)

How many chromosomes does a human ovum have?

23

Would a human skin cell undergo meiosis?

No, meiosis only occurs in reproductive cells.

How many cells are at the end of mitosis?

2 identical diploid cells

How many cells are at the end of meiosis?

4 different haploid cells

How many cells are at the end of meiosis I?

2 haploid daughter cells, each with 2 sister chromatids

Daughter cell

Cells produced as a result of cell division

Recombination

One chromosome breaks off and attaches to another chromosome during reproductive cell division

Nuclear membrane

Lipid bilayer that surrounds nucleus. Also called nuclear envelope.