Cellular Reproduction - Mitosis Notes

Prokaryotic vs. Eukaryotic Chromosomes

• Prokaryotic Chromosomes: Circular, smaller (less DNA), located in cytoplasm.

• Eukaryotic Chromosomes: Linear, more DNA, mostly in nucleus (some mitochondria).

Eukaryotic Chromosome Structure

• DNA packaged into chromosomes.

• Duplicated chromosome consists of "sister chromatids" joined by a "centromere".

• DNA is organized into nucleosomes with histone proteins, forming supercoils and coils.

Prokaryotic Cell Cycle: Binary Fission

• Asexual reproduction.

• DNA duplicates, cell membrane indents.

• Forms 2 daughter cells.

Eukaryotic Cell Cycle

• G1: Growth phase, normal cell function.

• S: DNA replication (synthesis).

• G2: Growth phase, preparation for mitosis.

• M: Active cell division (mitosis and cytokinesis).

• G0: Resting state, cell not dividing or preparing.

Eukaryotic Cell Cycle Checkpoints

• G1 checkpoint: Decides if DNA replication proceeds; if not, cell enters G0.

• G2 checkpoint: Checks DNA replication completeness; decides M phase entry.

• M (Spindle) checkpoint: Determines correct spindle fiber attachment to centromeres.

M-Phase: Mitosis and Cytokinesis

• Mitosis: Nuclear division, produces 2 identical daughter cells in somatic cells.

• Cytokinesis: Cellular division.

Phases of Mitosis

• Prophase: DNA condenses, chromosomes become visible, spindle forms, nuclear membrane breaks down.

• Metaphase: Chromosomes line up at the center of the cell.

• Anaphase: Sister chromatids separate and individual chromosomes move toward opposite poles.

• Telophase: Cell begins to divide, nuclear membranes reform.

Cytokinesis

• Animals: Cell membrane pinches in the center.

• Plants: A cell plate forms, followed by cell wall growth.