cells and microorganisms
TRANSCRIPT
Cells divide for a number of reasons:
1. To asexually reproduce(binary fission – prokaryotes)
2. To grow and repair tissues(mitosis – eukaryotes)
3. To form gametes (eggs and sperm) for sexual reproduction(meiosis – eukaryotes)
Cell Division
For bacteria (prokaryotes), cell division is a simple process.
Binary Fission Steps:
1. Single, circular chromosome replicates and fixes to themembrane
2. The membrane expands and grows apart
3. A new membrane forms between the two rings of DNA
4. Cells separate into two identical daughter cells, each with theirown circular chromosome
Binary Fission
Binary Fission
Describe Binary Fission in your own words. Include a diagram in your explanation.
Activity
In eukaryotes, cell division occurs by mitosis.
Mitosis produces two identical daughter cells that are diploid(they each have two copies of each chromosomes 2n).
Mitosis is used for growth and repair (eg: new skin, bloodcells, stomach lining).
After fertilisation, the zygote grows into a ball of identical cellsby mitosis.
Mitosis
Mitosis
Mitosis Steps:
1. Interphase: Cell grows and chromosomes replicate
2. Prophase: Duplicated chromosomes condense
3. Metaphase: Chromosome pairs align in the centre of the cell(metaphase plate)
4. Anaphase: Spindle fibres pull chromosomes to opposite ends ofthe cell
5. Telophase: Cell pinches in the middle (cleavage furrow)
6. Cytokinesis: Cells separate, forming two identical daughter cells
Prophase
Animal Plant
Chromatin condenses, chromosomes visible, nuclear membrane breaks down, spindle forms, nucleoli disappear
Metaphase
Animal Plant
Replicated chromosomes align at the equator with sister chromatids facing opposite poles. They attach to the spindle at the centromere.
Telophase and Cytokinesis
Animal Plant
Nuclear envelopes start to form around each new set of chromosome.Animals: The cell pinches in to separate the cytoplasm.
Plants: Cell wall forms between the two new cells.
Binary Fission vs Mitosis
Binary Fission MitosisProkaryotes Eukaryotes
No spindle formation Spindle formation
Chromosome attaches to membrane Chromosomes align at metaphase plate
Used for reproduction Used for growth and repair
INTENDED STUDENT LEARNING
Compare binary fission in prokaryotic cells with mitotic cell division in eukaryotic cells.
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