Chromosomes+mitosis-B1-cell biology

CHROMOSOMES CONTAIN GENETIC INFORMATION
* most cells in our body have a nucleus, containing your genetic information in the form of chromosomes.
* chromosomes are coiled up Lengths of DNA molecules.
* each chromosome carries a large number of genes. different genes control the development of different characteristics.
* body cells Normally you have two copies of each chromosome - one from the organism's 'mother', and the other from its 'father'.
* humans have two copies of chromosome 1, two copies of chromosome 2, etc.

THE CELL CYCLE MAKES NEW CELLS
* body cells in multicellular organisms divide to produce new cells in a series of stages called the cell cycle.
* the stage of the cell cycle when the cell divides is called mitosis.
* multicellular organisms use mitosis to grow or replace cells that have been damaged.
* the end of the cell cycle results in two new cells identical to the original cell with the same number of chromosomes.
* you need to know about the two main stages of the cell cycle:
- 1. in a cell that isn't dividing the DNA is all spread out in long strings. before it devised, the cell has to grow and increase the amount of subcellular structures such as mitochondria and ribosomes. (GROWTH & DNA REPLICATION)
- 2. it then duplicates its DNA So there's one copy for each new cell. The DNA forms X shaped chromosomes, where each 'arm' of the chromosome is an exact duplicate of the other. (GROWTH & REPLICATION)
- 3. once its contents and DNA have been copied, the cell is ready for mitosis.
- 4. the chromosomes line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome go to opposite ends of the cell.(MITOSIS)
- 5. membranes form around each of the sets of chromosomes. these become the nuclei of the two new cells - the nucleus has divided. (MITOSIS)
- 6. Lastly, the cytoplasm and cell membrane divide. (MITOSIS)
The cell has now produced two new daughter cells. the daughter cells contain exactly the same DNA- they're identical. Their DNA is also identical to the parent cell.