Chapter 8: Mitosis & Cancer

Prokaryotic Cell Cycle

• Prokaryotes utilize a single circle of DNA (chromosome).

• Cell division occurs via two stages: 1) DNA replication, 2) binary fission.

Eukaryotic Cell Cycle

• Two types of cell division in eukaryotes:

  • Mitosis (non-reproductive/somatic cells).

  • Meiosis (reproductive/germ-line cells).

• Divided into phases:

  • Interphase (G1, S, G2 phases).

  • G1: Growth.

  • S: DNA replication.

  • G2: Preparation for division.

  • M phase: Mitosis or Meiosis (chromosomes are separated).

  • C phase: Cytokinesis (cytoplasm division).

Chromosomes

• Eukaryotes have multiple linear chromosomes (pairs = homologous chromosomes).

• Cells with two of each type are diploid.

• Karyotype: organized display of chromosomes.

• Chromosomes replicate into sister chromatids before division, maintaining the total count.

• Comprised of chromatin (DNA + histones).

Cell Division Stages

1. Prophase: Chromosomes condense, nuclear envelope breaks down, spindle forms.

2. Metaphase: Chromosomes align at cell center.

3. Anaphase: Sister chromatids pull apart as they move to poles.

4. Telophase: Nuclear envelope re-forms and chromosomes decondense.

5. Cytokinesis: Cytoplasm divides into two daughter cells.

   • Animals: cleavage furrow.

   • Plants: cell plate formation.

Cancer Basics

• Cancer involves uncontrolled cell division leading to tumors.

• Tumors are malignant if they metastasize (spread).

• Regulated by checkpoints during cell cycle phases.

• Caused by mutations (changes in DNA sequences) often induced by carcinogens.

Types of Cancer Names

• Based on origin: organs (lung, breast) or cell types (carcinoma, sarcoma, leukemia, lymphoma).

Genes Involved in Cancer

• Proto-oncogenes: stimulate cell division; mutated to oncogenes.

• Tumor-suppressor genes: inhibit cell division; mutations lead to unchecked growth.

• Example: p53 gene (tumor suppressor) checks DNA integrity before division; mutations lead to cancer.