section 6: cell division & cellular organisation - topic 1: the cell cycle & mitosis Flashcards
what is the cell cycle?
the process that all body cells in multicellular organisms use to grow and divide.
what does the cell cycle consist of?
a period of cell growth and DNA replication - called interphase - and a period of cell division - called M phase.
what does M phase involve?
mitosis (nuclear division).
cytokinesis (cytoplasmic division).
what stages are interphase subdivided into?
3 growth stages - G1, S, G2.
what is the cell cycle regulated by?
checkpoints.
what are checkpoints?
they occur at key points during the cycle to make sure it’s okay for the process to continue.
what happens during G1?
cell grows.
new organelles and proteins are made.
what happens during G1 checkpoint?
the cell checks that the chemicals needed for replication are present, and for any damage to the DNA before entering S-phase.
what happens during S phase?
cell replicates its DNA, ready to divide by mitosis.
what happens during G2?
cell keeps growing.
proteins needed for cell division are made.
what happens during G2 checkpoint?
the cell checks whether all the DNA has been replicated without any damage. if it has, the cell can enter mitosis.
what are the two types of cell division?
mitosis and meiosis.
why is mitosis needed?
for the growth of multicellular organisms and for repairing damaged tissues.
what is the structure of the chromosomes at the start of mitosis?
the chromosomes are made of 2 strands joined in the middle by a centromere.
what are the separate strands of a chromosome called?
chromatids.
