Binary Fission

Stage 2 Biology: Cells as the Basis of Life

Cell Theory

  • Cells arise from pre-existing cells.

  • Cell division is essential for reproduction, growth, and repair.

DNA Replication

  • Essential for ensuring each daughter cell receives a full genome.

  • Failure to double DNA results in daughter cells receiving only a fraction of the genetic material.

Types of Cell Division

  • Binary fission: Asexual reproduction in prokaryotic cells.

  • Mitosis: Division in somatic (body) cells. Produces diploid cells (46 chromosomes).

  • Meiosis: Division in germ line cells (sperm or eggs). Produces haploid cells (23 chromosomes).

Binary Fission Process

  1. DNA replication via helicase and enzymes.

  2. DNA loops attach to cell membrane and segregate.

  3. Membrane pinches to form two daughter cells.

Comparison of Cell Division Types

Aspect

Binary Fission

Mitotic Division

Type of Cell

Prokaryotic

Eukaryotic

Replication

Yes

Yes

Nuclear Division

No

Yes

Chromosome Type

Single, circular

Many, linear

Cells Produced

Two

Two

Daughter Cells

Clones

Clones

Spindle Fibres

No

Yes

Growth Potential

Exponential

Exponential

Mitosis Overview

  • Phases of Mitosis:

    1. Interphase: DNA is chromatin.

    2. Prophase: Chromatin condenses, chromosomes become visible.

    3. Metaphase: Chromosomes line up, spindle fibres attach.

    4. Anaphase: Sister chromatids separate to opposite poles.

    5. Telophase: Nuclear membranes reform, chromosomes decondense.

    6. Cytokinesis: Cytoplasm divides, forming two identical daughter cells.

Key Details of Mitosis

  • Chromosomes consist of two sister chromatids.

  • Cytokinesis mechanism differs in animal (cell membrane pinch) vs. plant cells (cell plate formation).

Genetic Outcomes

  • Daughter cells from both mitosis and binary fission are genetically identical to parent cells.