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Cell Reproduction and Cancer Overview

Apr 25, 2025

Lecture 32: Cell Reproduction and Cancer

Key Topics

  • Eukaryotic Cell Cycle
  • Cell Cycle Regulation and Checkpoints
  • Cancer: Definition and Causes
  • Mutations Leading to Cancer
  • Proto-oncogenes and Oncogenes
  • Tumor Suppressor Genes/Proteins (p53)

Eukaryotic Cell Cycle

  • Highly regulated by proteins.
  • Cells should only divide when needed and capable.
  • Checkpoints ensure proper division.

Cancer

  • Definition: Uncontrolled, harmful cell growth.
  • Causes: Failures in cell cycle control proteins.

Causes of Faulty Proteins

  • Mutations in DNA causing defective proteins.
  • Mutations from unrepaired DNA damage.

Proto-oncogenes and Oncogenes

  • Proto-oncogenes: Normal genes involved in cell cycle.
  • Oncogenes: Mutated proto-oncogenes that cause cancer.

Tumor Suppressor Genes/Proteins

  • Prevent mutations and suppress tumor formation.
  • p53: Key protein in DNA repair and apoptosis.
    • Patrols for DNA damage.
    • Can repair damage or trigger apoptosis if damage is irreparable.

Importance of p53

  • Mutations in p53 can lead to cancer.
  • p53 mutation present in about 50% of cancers.
  • Redundancy and backup systems exist, but failure in key areas like p53 gene can lead to accumulation of oncogenes.

Chapter 11: Sexual Reproduction and Meiosis

Sexual Reproduction Overview

  • Increases genetic diversity compared to asexual reproduction.
  • Zygote Formation: Sperm (1n) + Egg (1n) = Zygote (2n).

Diploid and Haploid Cells

  • Diploid (2n): Two copies of each chromosome.
  • Haploid (1n): One copy of each chromosome.

Meiosis

  • Process to create haploid cells from diploid germ cells.
  • Consists of two rounds of division (Meiosis I and II).

Meiosis I

  • Prophase I: Chromosomes condense, tetrads form via synapsis.
  • Tetrad Formation: Homologous chromosomes pair up.
  • Crossover: Exchange of genetic material increases variation.
  • Metaphase I: Tetrads align randomly at the cell equator.
  • Anaphase I: Tetrads are pulled apart, but sister chromatids remain together.
  • Telophase I and Cytokinesis: Cells divide, resulting in haploid cells with replicated DNA.

Meiosis II

  • Similar to mitosis.
  • Sister chromatids are separated.
  • Results in four haploid cells (gametes).

Importance of Meiosis

  • Generates genetic variation through crossover and random assortment.
  • Essential for sexual reproduction.

Summary of Meiosis

  • Interphase followed by two rounds of division.
  • Each division results in cells that reduce chromosome number.
  • End result is four genetically diverse haploid cells.

Visual Aids Suggested

  • Draw or refer to diagrams illustrating differences between mitosis and meiosis.
  • Use colored markers to differentiate homologous chromosomes and sister chromatids.

These notes summarize the critical concepts of cell reproduction, the basis of cancer development, and the mechanisms of sexual reproduction through meiosis. Understanding these processes is crucial for comprehending how genetic information is passed and how abnormalities can lead to diseases like cancer.

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