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CREATED BY V.O NGWENYA200728427
Chromosomes form when the chromatin network in the nucleus of the cell, coil up, shortens and thickens.
Each organism has a specific amount of chromosomes. All humans have 46 chromosomes. These chromosomes are arranged in identical pairs
called homologous chromosome pairs – Therefore humans have 23 homologous pairs of
chromosomes. These chromosomes is only visible during cell division
processes. One chromosome consist of 2 chromatids and one
centromere that attach the chromatids together. Each chromatid consist of genes which in turn consist of
DNA.
X and Y chromosomes: gonosomes/sex-chromosomes
Colored bands represents different genes
The cell cycle includes the following phases:
Interphase (include G1- , S- [DNA synthesis] and G2 phase)
Prophase Metaphase Anaphase Telophase
The result is 2 identical cells.
Allow an organism to grow.Repairs damaged
cells/tissue.Replace dead cells/tissue.Reproduction in some
simple organisms.
In all somatic cells (include all body cells and excludes the sex cells – sperm/egg cells)
CONSIST OF A FEW PHASES:
INTERPHASE
PROPHASE
METAPHASE
ANAPHASE
TELOPHASE
Cell builds up enough energy for division process.
DNA replication occurs Cell look normal, like before division
Nuclear envelope and nucleolus disappear.
Chromatin become more tightly coiled, and condenses into individual chromosomes. Chromosomes arrange randomly in the cell.
Centrioli move to opposite poles, with spindle fibers stretching between them.
The centrioli reached the opposite poles with the spindle fibers in between.
The chromosomes arrange randomly on the equator, each single chromosome attaching to a separate spindle fiber by means of the centromere.
The spindle fibers pull tight. The centromers attaching the chromatids of
the chromosomes split in half. Daughter chromosomes move to opposite
poles.
Daughter chromosomes reach poles.
Nuclear envelope surrounds chromosomes.
Nucleolus reappear at each pole. Chromosomes become less
condense forming chromatin. Two identical nuclei has been
formed
Invagination of the cytoplasm and plasma membrane occurs. (Cleavage furrow forms in animal cells and a cytoplasmic plate forms in plant cells)
Continues until the cell in divided into 2 separate cells. (Identical to one another and to the original cell)