Cell Division

Mitosis

Meiosis

Growth

is a permanent increase in size accompanied by cell division and differentiation to form tissues & organs

Mitosis take places during growth

is a form of nuclear divisions that produces daughter nuclei containing the same number of chromosomes as parent nucleus. (genetically similar)

Cell Cycle

I nterphase

M itosis

C ytokinesis

the non-dividing stage of a cell

cells still carry out cell activities like absorbing nutrients

Before each cell divides, chromatin threads replicate

Two chromatin thread attached to the same centromere so they are called 'sister chromtids'

Furrows / cleavage appear in the cytoplasm between the two nuclei

The furrows deepen and 2 identical daughter cells are produced

is a form of nuclear division that produces daughter nuclei containing half the number of chromosomes s the parent nucleus

TWO nuclear divisions occur so there are 2 divisions in meiosis : meiosis I and meiosis II

meiosis can be summarised by I M C M C

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However, for meiosis at Prophase I, crossing over occurs.

Homologous chromosomes (a pair of chromosomes, one from the father and the other from the mother) pair along their whole length

Chromatids cross and twist around one another and the point where they cross is called a chiasma.

Importance of mitosis

Mitosis enables growth of an organism

Mitosis is needed for the repair & growth of worn-out parts

Mitosis allows asexual reproduction to occur.

Importance of meiosis

Meiosis produces haploid gametes. Gametes are reproductive cells that contain haploid number of chromosomes.

Meiosis results in variation in the gametes produced

Variation occurs because of 1. crossing over 2. independent assortment of chromosomes 3. random fertilisation

Variations increase the chances of survival of the species during changes in the environment

Differences