Cell Division

Mitosis

Meiosis

The Cell Cycle

The Cell Cycle

•G1 (Growth Stage) – the organelles start to double in number.• S (Synthesis Stage) – the DNA strands replicate.•G2 (Growth Stage) – more protein is made.

Mitosis• A process of cell division herein

two new daughter cells receive exactly the same number of chromosomes as the parent cell.• It includes four stages namely:

Prophase, Metaphase, Anaphase and Telophase.

The Process of Mitosis

Prophase• The nucleus

disappears.• The nuclear

membranes breakdown and disappears.

• Centrioles move toward the opposite poles.

Metaphase• Chromosomes

move toward and alignment at the center of the cell.

• Centromere of chromosomes attaches itself to a spindle fiber.

Anaphase• Chromatids

separate and each pair is pulled to each pole.• Cell membrane

begins to pinch together at the cell’s center.

Telophase• The nucleolus and

nuclear membrane appears.

• Chromosomes uncoil and become chromatin.

• Cell membrane completely pinches and centrioles replicate.

Meiosis• A cell division of diploid cells that produces haploid cells like sex cells.• It require to nuclear division: Meiosis I and Meiosis II.

Process of Meiosis

Meiosis IProphase I • The nucleus membrane and nucleolus disappears

• Spindle fibers begin to form.

Metaphase I • Crossing – over between the homologue pair happens• Spindle fibers completely form

Anaphase I • Homologues of each pair split and move to the opposite sides, the chromosomes number on each side is half the original number

Telophase I • The nucleolus appears• The nuclear membrane form• Pinching of the cell membrane is completed so there are

two ne cells

Meiosis IIProphase II • Spindle fibers begin to form

• The nuclear membrane breaks

Metaphase II • The chromosomes align at the center• Spindle fibers form completely

Anaphase II • The chromatids of each chromosomes are pulled apart and move toward opposite sides

Telophase II • The nuclear membrane appears

References

• Olivares, Maria, et. al. Science and Technology for the modern world. Textbook for second year. 2003. DIWA Scholastic Press Inc. Makati City