Chapter 10: Cell Reproduction

Key Concepts

• Cell Division: Process where cells come from pre-existing cells, dividing and multiplying.
• Mitosis and Cytokinesis: Processes by which a single cell becomes multiple cells.
• Functions of Cell Division: Includes reproduction in single-celled organisms, growth, maintenance, and repair in multicellular organisms.

Cell Division in Organisms

• Single-Celled Organisms: Reproduce through cell division, population size increases through division.
• Multi-Cellular Organisms: Utilize cell division for growth and repair, sometimes for asexual reproduction through processes like budding.

Genome and Chromosomes

• Genomic Duplication: Essential for cell division, ensuring each new cell has a full set of DNA.
• Chromosome Count in Humans: 46 chromosomes total, 22 pairs plus 2 sex chromosomes.
• DNA: Linear chromosomes in eukaryotes, circular in prokaryotes, and often contains regions that are not used or turned off.

Prokaryotic Cell Division

• Binary Fission: Division method for prokaryotes starting at an origin of replication, involving proteins like FtsZ.
• Cell Elongation: Necessary for division, involving replication of DNA and cell components.

Eukaryotic Cell Division

• Mitotic Process: More complex due to linear chromosomes; involves steps to replicate and separate genetic material.
• Cell Cycle: Includes interphase (G1, S, G2) and the mitotic phase.
• Mitosis Stages: Prophase, prometaphase, metaphase, anaphase, telophase.

Chromosomal Structures

• Chromatin vs Chromosome: Chromatin is loosely packed DNA; chromosomes are condensed, visible during cell division.
• Sister Chromatids and Homologous Chromosomes: Key terms for understanding genetic replication and separation.
• Karyotype: Displays ordered chromosomes by size, visualizing chromosomal arrangement.

Regulatory Mechanisms

• Checkpoints: G1, G2, and M checkpoints ensure proper cell division by checking for DNA damage and proper attachment of spindle fibers.
• Positive and Negative Regulators: Ensure cells only divide when appropriate, involving proteins like cyclins and CDKs.

Cancer Connection

• Uncontrolled Cell Growth: Result of mutations in genes, particularly affecting regulatory proteins.
• Proto-oncogenes and Tumor Suppressor Genes: Key players in cell cycle regulation and cancer development.
• External Factors: Tobacco smoke, UV radiation, genetic predispositions, and certain infections can increase cancer risk.

Summary

Cell reproduction is essential for growth, maintenance, and repair in living organisms. It involves complex processes regulated by various checkpoints and proteins, ensuring that cells divide only when conditions are right. Understanding these processes provides insight into how cancers can develop when these regulatory mechanisms fail.