Only $2.99/month

Terms in this set (37)

Mitosis is cell division that preserves the original parental number of chromosomes in the 2 daughter cells.

Functions of mitotic cell division:
1. Asexual reproduction: unicellular protists like amoeba example budding of unicellular fungi like yeast.
2. Development - cleavage
3. Tissue growth and repair.

MITOSIS
PROPHASE - Centrosomes move to opposite poles. Spindle microtubules and asters begin to form. Replicated chromosomes begin to condense.

PROMETAPHASE - Nuclear membrane breaks down because sister chromatids will need to separate into two daughter cells.
A kinetochore (kt) protein-complex appears at each centromere and attaches the centromeres of sister chromatids to spindle fibers.
The spindle is now complete.
Non-kt microtubules go pole to pole.
Kt molecules go pole to kt.
Aster microtubules "anchor" the centrosome to cell membrane.

METAPHASE - Spindle microtubules moves the chromosomes. Chromosomes line up along the midline/metaphase plate/equator.
Note++ The two sister chromatids of replicated chromosome face opposite poles

ANAPHASE - Centromeres split. Spindle microtubules shorten and pull apart sister chromatids toward opposite poles. Once separated each sister chromatid is now called a chromosome.
Note spindle microtubules shorten at the the kinetochore and pull chromosomes toward pole of the cell breaking the centromere apart.

TELOPHASE - Spindle disassembles. Nuclear membrane reforms. Mitosis = nuclear division.
Nuclear division is now complete.

CYTOKINESIS - Last part of the M phase. Cell membrane pinches together at the cleavage furrow. Cytoplasm division is now complete. Cell division is now complete.
Result: 2 daughter cells. Each has the same number of chromosomes as the parent cell and each has identical DNA sequence as the parent cell.

Daughter cells have the SAME NUMBER OF CHROMOSOMES AS THE PARENT CELL AND ARE GENETICALLY IDENTICAL.
Meiotic cell division: a diploid cell divides to form 4 haploid daughter cells. Requires two cell divisions and reduces the diploid chromosome number in half. A REDUCTION DIVISION - REDUCES THE CELL FROM 2N TO N.

PROPHASE 1 - SYNAPSIS, homologous chromosomes pair up and form tetrads
CROSSING OVER - non-sister chromatids in a tetrad exchange equivalent segments at a CHIASMA.
Centrosomes move to opposite poles. Spindle microtubules and asters begin to form. Replicated chromosomes begin to condense.

METAPHASE I - TETRADS line up at the metaphase plate. PAIR not individual chromosomes. Therefore. A diploid number of 6 in G1 yields 12 chromosomes after S which form 3 tetrads, 6 homologous chromosomes.
Meaning that at metaphase 1 there is still only 6 chromosomes.

ANAPHASE I - Separation of homologous chromosomes. The tetrads are broken up! Still two chromosomes in each pair.

TELOPHASE 1 AND CYTOKINESIS - Ends with 2 haploid cells but sister chromatids are still attached. Each cell has three homologous pairs, therefore each has three chromosomes. DO NOT UNDERGO INTERPHASE. A nuclear envelope reforms around each chromosome set, the spindle disappears, and cytokinesis follows. In animal cells, cytokinesis involves the formation of a cleavage furrow, resulting in the pinching of the cell into two cells. After cytokinesis, each of the two progeny cells has a nucleus with a haploid set of replicated chromosomes.

PROPHASE II - Centrosomes move to opposite poles. Spindle microtubules and asters begin to form. chromosomes begin to condense.

METAPHASE II - Attached sister chromatids line up at the midline. Note orientation to the poles.

ANAPHASE II - Sister chromatids separate

TELOPHASE II AND CYTOKINESIS - Nuclear envelope reforms, cleavage occurs. 4 haploid daughter cells.