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Flashcards in Cell Cycle Deck (11):

What stages are in the cell cycle?

Interphase (G1,S,G2), mitosis and cytokinesis


What happens in interphase?

In actively dividing tissue, cells in interphase appear to be doing nothing, but actually this is a very active period of growth and metabolism.
G1 is the first growth stage - the cell makes new proteins.


What happens in prophase?

The chromosomes condense (coil up) and become visible as two joined chromatids. Spindle fibres attach to the chromosomes at centromeres. The nuclear membrane disintegrates.


What happens in metaphase?

Spindle fibres move the chromosomes so that they line up on the metaphase plate at the equator of the cell.


What happens in anaphase?

The spindle fibres pull sister chromosomes apart. Once they are separated, the chromatids are called chromosomes in their own right.


What happens in telophase?

The sepRated chromosomes are pulled by the spindle fibres to opposite poles to form daughter nuclei. The chromosomes start to uncoil and nuclear membrane is mad again.


What happens in cytokinesis?

The membrane is pulled about in by part of the cytoskeleton to divide the cytoplasm to form two daughter cells. Plant cells have to form a middle lamella and cell wall before the membrane is made.


What is the mitotic index?

The percentage of cells undergoing mitosis. If a tissue sample has an unusual high mitotic index, this may indicate a developing tumour.


What happens in the G1 checkpoint?

The checkpoint is near the end of G1. Here the cell size is monitore. There has to be sufficient cells mass to form two daughter cells. This checkpoint controls entry to the S phase.


What happens in the G2 checkpoint?

It is at the end of G2. This checks the success of DNA replication to make sure each daughter cell can receive a complete copy of DNA. This checkpoint controls entry to mitosis using a protein called Complex called mitosis-promoting factor (MPF). As the name implies, mitosis will only be triggered if sufficient MPF is present.


What happens in the M checkpoint?

It happens during the M phase during metaphase. This monitors the chromosome alignment to ensure each daughter cell receives one chromatid each chromosome. Third checkpoint controls the entry to anaphase. Thus, it triggers the exit from mitosis and start of cytokinesis.