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.