Cell and Nuclear Division

Cell division that results in a daughter cell with a complete set of identical instructions is called mitosis.

What is mitosis important for?

• Production of genetically identical cells
• Growth (Replacement of cells)
• Repair of tissues
• Asexual reproduction

Cell cycle

During S phase DNA replicates: 

1. Original DNA splits into 2 strands breaking H-bonds
2. Nucleotides join up to the template strand
3. Pair up according to the complementary base pair rules (H-bonds reform)
4. 2 new, identical helices formed

Prophase:

(Centriole replicates before prophase)

• Chromosomes coil up becoming shorter and thicker 
• Nuclear envelope breaks into vesicles 
• Nucleolus forms parts of chromosomes
• Centrioles move to opposite poles and form spindles

Metaphase:

• Each centriole reaches a pole 
• Centrioles organise production of spindle microtubules
• Chromosomes line up attached by the centromere along the equator of the spindle

Anaphase:

• Chromatids move to opposite poles, centromeres first, pulled by the microtubules

Telophase:

• Nuclear envelope and nucleolus reform
• Chromatids uncoil to form chromatin
• Beginning of cytokinesis
• Centriole will replicate during interphase before the next nuclear division

Cytokinesis= the division of the cytoplasm and cell into two by constriction from the edges of the cell

Chromosome=A structure formed from DNA that condenses in a nucleus before mitosis can occur

Chromatin= Material containing DNA and proteins

Sister Chromatid= An arm of a chromosome. These are joined by a centromere and are separated and pulled to opposite poles

Centromere= A structure which allows chromosomes to be attached to spindle fibres at the equator

Spindle fibres= Fibres formed from the centrioles at opposite ends of the poles which chromosomes are pulled along

Equator= The metaphase plate where chromosomes align, attach to spindle fibres and sister chromatids are separated. A cleavage furrow or cell plate is formed here during cytokinesis

Centriole= Replicate and are located at opposite poles of the cell. Spindle fibres form from these

Base pair rules= Rules stating which nucleotide bases join together. Crucial during DNA replication in interphase. C=G, A=T