Chromosomes and Mitosis Flashcards
What are chromosomes ?
1) most cells in your body have a nucleus . The nucleus contains your genetic material in the form of chromosomes
2) Chromosomes are coiled up lengths of DNA molecules
3) Each chromosome contains a large number of genes. Different genes control the development of different characteristics
4) Body cells normally have two copies of each chromosomes - one from organisms ‘mother’ and one from its ‘father’ . Humans have two copies of chromosomes 1 and two copies of chromosomes 2
5) 23 pairs of chromosomes from human cell
What is mitosis ?
1) body cells in multicellular organisms divide to produce new cells as part of cell cycle
2) stage of cell cycle when cell divides = mitosis
Why do multicellular organisms use mitosis ?
grow, replace cells that have been damaged.
End of cell cycle results in …
two new cells identical to original cell with same number of chromosomes
Stage 1 Growth and DNA replication
1) In a cell that’s no dividing, DNA is spread out in long strings
2) Before division , cells grows and increases in amount of subcellular structures such as ribosomes
3) then duplicates in DNA - one copy for each new cell . DNA copied and forms x shaped chromosomes. Each arm of DNA is exact duplicate of the other.
Stage 2 Mitosis
1) chromosomes line up across the centre, cell fibres pull them apart in opposite direction so arms of each chromosome go to opposite ends of the cell
2) membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells = the nucleus has divided
3) cytoplasm and cell membrane divide
The cell has formed two new daughter cells, exact same DNA and identical also to parent cell
