1.5.2: Mitosis, Meiosis, and Cytokinesis in Plants and Animals

Interphase

90% of cells life, DNA is copied; 3 stages

mitotic phase

phase where parent cell splits into 2 identical cells

What are the 4 subphases of the mitotic phase?

prophase, metaphase, anaphase, teophase

prophase

chromosomes condense

metaphase

chromosomes align on metaphase plate

anaphase

chromosomes pulled to poles

teophase

chromosomes decondense

Meiosis

forms 4 unique 1n cells, stem & eggs; 2 parts (meiosis I & Meiosis II)

Meiosis I

stages in same order as mitosis with the important difference of having crossing over occurring during Prophase I, causing new combinations as a result

Meiosis II

Same as in mitosis & meiosis I, but chromosomes have been through crossing over; end product is 4 haploid cells, instead of the 2 that result from mitosis & meiosis I

Crossing over

process unique to meiosis, where homologous chromosomes exchange genetic material, increasing genetic diversity.

What are the 3 stages of interphase?

G1 Phase (1st gap), S phase (Synthesis of DNA), G2 Phase (second gap)

G1 Phase

The cell is accumulating the building blocks of chromosomal DNA and the associated proteins as well as accumulating sufficient energy reserves to complete the task of replicating each chromosome in the nucleus.

S phase

DNA replication can proceed through the mechanisms that result in the formation of identical pairs of DNA molecules—sister chromatids—that are firmly attached to the centromeric region; centrosome is duplicated during the S phase; The two centrosomes will give rise to the mitotic spindle, the apparatus that orchestrates the movement of chromosomes during mitosis.

G2 Phase

the cell replenishes its energy stores and synthesizes proteins necessary for chromosome manipulation.

Karyokinesis

divided into a series of phases—prophase, prometaphase, metaphase, anaphase, and telophase—that result in the division of the cell nucleus

Cytokinesis

second main stage of the mitotic phase during which cell division is completed via the physical separation of the cytoplasmic components into two daughter cells

G0 phase

The cell is in a quiescent (inactive) stage that occurs when cells exit the cell cycle

____ is the part of a cell reproduction cycle that results in identical daughter nuclei that are also genetically identical to the original parent nucleus

Mitosis ; both the parent and the daughter nuclei are at the same ploidy level—diploid for most plants and animals.

In ____ the starting nucleus is always diploid and the nuclei that result at the end of a meiotic cell division are haploid.

Meiosis

Prophase II

If the chromosomes decondensed in telophase I, they condense again. If nuclear envelopes were formed, they fragment into vesicles. The centrosomes that were duplicated during interkinesis move away from each other toward opposite poles, and new spindles are formed.

Prometaphase II

The nuclear envelopes are completely broken down, and the spindle is fully formed. Each sister chromatid forms an individual kinetochore that attaches to microtubules from opposite poles.

Metaphase II

The sister chromatids are maximally condensed and aligned at the equator of the cell.

Anaphase II

The sister chromatids are pulled apart by the kinetochore microtubules and move toward opposite poles. Non-kinetochore microtubules elongate the cell

Telophase II

The chromosomes arrive at opposite poles and begin to decondense. Nuclear envelopes form around the chromosomes.

Difference between Mitosis and Meiosis

The nuclei resulting from a mitotic division are genetically identical to the original nucleus. They have the same number of sets of chromosomes, one set in the case of haploid cells and two sets in the case of diploid cells; meiosis consists of two nuclear divisions resulting in four nuclei that are usually partitioned into four new cells. The nuclei resulting from meiosis are not genetically identical and they contain one chromosome set only