08_Lecture_Presentation

Cancer and Cell Division

  • Cancer cells originate from normal cells due to genetic mutations affecting division regulation.

  • Resulting uncontrolled division can lead to tissue invasion, organ function disruption, and death.

  • Normal cell division is essential for life processes.

Cell Division and Reproduction

Overview

  • Cell division is vital in the reproduction of cells and organisms; preexisting cells give rise to new ones.

  • Asexual reproduction yields genetically identical offspring, while sexual reproduction results in genetic diversity.

Prokaryotic Cell Division

  • Prokaryotes reproduce asexually via binary fission:

    • Involves chromosome replication, cell elongation, and membrane pinching, leading to two daughter cells.

Eukaryotic Cell Cycle and Mitosis

Chromosome Duplication

  • Eukaryotic chromosomes are complex, with many genes organized into multiple chromosomes.

  • Chromosomes are duplicated and prepare for division, creating sister chromatids.

Cell Cycle Phases

  • Cell cycle includes:

    • G1 (growth phase)

    • S (DNA synthesis)

    • G2 (second growth phase)

    • M (mitosis)

Mitosis Process

  • Mitosis separates sister chromatids into daughter nuclei:

    • A mitotic spindle organizes and distributes chromosomes to new cells.

Cytokinesis

  • Final step of cell division:

    • In animals, involves cleavage furrow formation.

    • In plants, forms a cell plate leading to cell division.

Regulation of Cell Division

  • Dividing cells require anchorage and typically stop when in contact with each other.

  • Growth factors influence cell cycle checkpoints, playing a role in division regulation.

Cancer and Tumors

  • Cancer results in excessive division forming tumors, especially malignant ones capable of invading tissues.

  • Treatments like radiation/chemotherapy interfere with cell division processes.

Meiosis and Genetic Variation

Homologous Chromosomes

  • Somatic cells contain pairs of homologous chromosomes (e.g., humans have 46 total).

  • Meiosis produces haploid gametes from diploid parent cells.

Process of Meiosis

  • Meiosis I: Homologous chromosomes separate, leading to two haploid cells.

  • Meiosis II: Sister chromatids separate, resulting in four genetically unique haploid gametes.

Chromosome Number and Structure

  • Nondisjunction can create gametes with abnormal chromosome counts.

  • Karyotyping analyzes chromosomes for abnormalities, such as in Down syndrome (Trisomy 21).

Nondisjunction and Genetic Disorders

  • Nondisjunction during meiosis leads to gametes with incorrect chromosome numbers:

    • Resulting conditions can affect development and health.

Connections to Evolution

  • Nondisjunction can lead to polyploid organisms, contributing to speciation.

  • Chromosomal changes may develop through structural alterations, leading to genetic disorders or cancer.

Conclusion

  • Understanding cell division, including processes like mitosis and meiosis, is critical in biology, especially in aspects of reproduction and diseases such as cancer.