Cell Division and Mitosis

• Cell division is essential for growth, development, and repair in organisms.
• Cells divide to maintain a small size, which ensures efficient transport of materials.

Cell Cycle

• The cell cycle consists of Interphase, Mitosis, and Cytokinesis
• Interphase prepares the cell for division through three phases: G1, S, and G2.
  • G1 phase involves cell growth.
  • S phase involves DNA replication.
  • G2 phase prepares the cell for division and replicates organelles.
• Mitosis divides the nucleus
  • Mitosis includes prophase, metaphase, anaphase, and telophase.
• Cytokinesis divides the cytoplasm.

Mitosis Checkpoints

• G1 checkpoint ensures adequate space and resources for new cells.
• G2 checkpoint verifies accurate DNA replication.
• M checkpoint confirms spindle fiber attachment to sister chromatids.

Cytokinesis

• Cytokinesis purpose is to divide the cytoplasm
• Animal cells divide via a pinching furrow.
• Plant cells divide via a cell plate.

Cancer and the Cell Cycle

• Cancer involves uncontrolled cell division, bypassing cell cycle checkpoints.
• Cancer disrupts the body's homeostasis
• Treatments include surgery, chemotherapy, and radiotherapy.

Cell Differentiation

• Stem cells differentiate into specific cell types.
• Embryonic stem cells can become any cell type.
• Adult stem cells can become only one cell type.
• Growth factors program stem cell differentiation.

Binary Fission vs. Mitosis

• Binary fission occurs in bacteria (prokaryotic cells).
  • DNA replicates before division
  • Circular DNA is present.
  • Creates two genetically identical cells.
• Mitosis occurs in plants and animals (eukaryotic cells).
  • Linear DNA is present.
  • Chromatin condenses into chromosomes before division.
  • The nuclear membrane breaks apart before DNA moves

Genetic Variation in Bacteria

• Bacteria increase genetic variation by:
  • Picking up plasmids from the environment
  • Exchanging plasmids with another bacterial cell
  • Mutations

Antibiotic Resistance

• Bacteria with resistance genes survive and reproduce more in the presence of antibiotics.
• To reduce resistance:
  • Use antibiotics only when necessary.
  • Avoid antibiotics for viral infections.
  • Reduce antibiotic use in meat production.

Bactericide lab

• Testing the effectiveness of bactericides on killing bacteria by measuring the diameter of the zone of inhibition in cm and mm

Meiosis

• Meiosis is the division of a diploid cell into four haploid cells.
• Haploid cells have half the chromosomes; diploid cells have a full set.
• Meiosis produces gametes (sperm and egg), which fuse during fertilization to form a diploid zygote. DNA replication precedes meiosis during interphase.

Stages of Meiosis

• Meiosis I:
  • Prophase I: crossing-over occurs.
  • Metaphase I: homologous chromosomes line up.
  • Anaphase I: homologous chromosomes separate.
  • Telophase I/Cytokinesis: nuclear membrane reforms.
• Meiosis II:
  • Prophase II: nuclear membrane breaks apart
  • Metaphase II: sister chromatids line up.
  • Anaphase II: sister chromatids separate.
  • Telophase II/Cytokinesis: four haploid cells form.

Genetic Variation in Sexually Reproducing Organisms

• Crossing-over during meiosis.
• Independent assortment during metaphase I.
• Random fertilization of sperm and egg.

Nondisjunction

• Nondisjunction is the incorrect chromosome separation during meiosis.
  • In meiosis I: 2 gametes with n+1 chromosomes and 2 with n-1.
  • In meiosis II: 2 normal gametes with n chromosomes, 1 with n+1, and 1 with n-1.
• Nondisjunction causes genetic disorders like Down Syndrome, Turner Syndrome, and Klinefelter Syndrome.