Chromosomes are condensed DNA.

• The Centromere is part of chromosome where sister chromatids are held together.

• 1chromosome = 2 chromatids

MITOSIS (ASEXUAL REPRODUCTION)

• Mitosis’s function is to grow and repair/maintain body.

  • A cell grows, and divides, and repeats during its life.

• 1 parent cell (46 chromosomes) produces 2 identical daughter cells (46 chromosomes each).

• Your cells do not divide (perform mitosis) continually. Most of the time, they are in interphase.

• Cancer is when cells uncontrollably divide.

INTERPHASE (PRE MITOSIS)

• The cell grows in size and performs regular functions.

• Chromosomes are replicated (doubled).

FOUR STAGES OF MITOSIS

• PMAT : Prophase, Metaphase, Anaphase, Telophase

• Prophase

  • Centrioles (poles) appear and move to opposite ends of cell.

  • Spindle fibers form between the poles.

• Metaphase

  • Chromatids line up in the middle of the cell and attach to the spindle fibers.

• Anaphase

  • Chromatids separate and begin to move to opposite ends of of the cell.

• Telophase

  • Two new nuclei form and the chromosomes appear as chromatin (threads rather than rods).

  • Mitosis ends.

Cytokinesis

• Cell membrane moves inward to create two daughter cells (each with its own nucleus and identical chromosomes).

MEIOSIS (SEXUAL REPRODUCTION)

• Prophase 1

  • Chromosomes line up with their homologous pairs.

    • Homologous chromosomes are 2 chromosomes that are about the same size & have the same gene type in the same place.

  • Crossing over occurs (homologous pairs transfer their genetic info, creating recombinant chromosomes).

• Metaphase 1

  • Chromosomes line up in the middle of the cell in pairs and attach to spindle fibers.

• Anaphase 1

  • The spindle fibers pull the homologous chromosomes apart and they move to opposite ends of the cell.

• Telophase 1 and Cytokinesis (ends meiosis one)

  • The nuclear membranes reform around the chromosomes, the two cells are separate.

• Prophase 2

  • The two haploid cells start to go through meiosis 2.

  • The cells nuclear membrane breaks back down, and spindle fibers begin to form.

• Metaphase 2

  • Chromosomes line up in the middle of the cell and attach to spindle fibers (single file).

• Anaphase 2

  • Sister chromatids separate and are pulled to opposite sides of the cell by spindle fibers.

• Telophase 2 and Cytokinesis

  • The nuclear membranes reforms.

  • Four new haploid cells (23 chromosomes) have formed!

  • These cells are gametes, and each one is unique and different from each other (NO identical cells, unlike cells from mitosis).

• Nondisjunction occurs when chromosomes don't separate correctly.

  • A cell may receive too many or too little chromosomes in the separation.