Biology Exam 3

process of cell division (occurs in actively dividing tissues; growth and development)

produce two cells (daughter cells) from one

a full complement of DNA and all the required organelles

how each daughter cell gets a full complement of DNA

Interphase
Prophase
Metaphase
Anaphase
Telophase

- sometimes called the “resting” phase
- nucleus is well defined with nucleoli
- chromosomes are not visible
- DNA is replicated during this phase, but the cell exhibits no outward manifestation of this process
- centrosomes duplicates and both are located to the same side of the nucleus

- nuclear membrane disappears
- nucleoli disappear
- chromosomes condense, each is now comprised of two (sister) chromatids that are held together by a centromere
- centrosomes begin to migrate to the poles of the cell and the mitotic spindle begins to form

- fully formed spindle at the cellular poles
- duplicated chromosomes align along the equatorial plate
- spindle fibers attach to the a special region of centromere called the kinetochore (each chromatid now has a centromere and kinetochore)

- spindle fibers contract and pull sister chromatids apart
- each chromatids is now called a chromosome
- chromosomes move toward the poles of the cell

- nuclear membranes begins to form around the chromosomes
- chromosomes decondense somewhat
- cytokinesis occurs
animal - cleavage furrow
plants - formation of a cell plate

1. G1 - growth phase (cell enlargement)
2. S (DNA replication; chromosomes copied)
3. G2 (cell enlargement continues)

• mitosis (karyokinesis) - division of the nucleus
• cytokinesis - division of the cytoplasm

• Events that occur during the cell cycle are regulated by a group of proteins called protein kinases
• The activity of protein kinases moves the cell through checkpoints in the cycle

Mitosis and Meiosis

produces daughter cells which maintain a standard number of chromosomes; two daughter cells result

produces daughter cells which have half the number of chromosomes; four daughter cells result