chromosomes and mitosis Flashcards
what are chromosomes
most cells in our body have a nucleus. the nucleus contains genetic our genetic material in the form of chromosomes.
chromosomes are coiled up lengths of DNA molecules
what chromosomes carry
each chromosomes carries large number of genes. different genes control the development of different characteristics
how many chromosomes does the human body have
Humans have 46 chromosomes in each cell, which is made up of 23 pairs of chromosomes
what is the cell cycle
body cells in multicellular organisms divide to produce new cells as part of a series called the cell cycle
what are the two main stages of the cell cycle
(growth and DNA replication) and (mitosis)
what happens during growth and DNA replication
1) in a cell that is not dividing, the DNA is all spread out in long strings
2) before it divides, the cell has to grow and increase the amount of subcellular structures such as mitochondria and ribosomes
3)it then duplicates its DNA - so there is on copy for each new cell. the DNA is copies and form X-shaped chromosomes. each ‘arm’ of the chromosome is an exact duplicate of the other
what happens during mitosis
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 chromosomes go the opposite ends of the cell
5) membranes form around each of the sets of chromosomes. these become the nuclei of the two new cells - the nucleus has divided
6) lastly, the cytoplasm and cell membrane divide. the cell has now produced two new daughter cells. the daughter cells contain exactly the same DNA - they are identical. their DNA is also identical to the parent cell.
