mitosis Flashcards
what happens in mitosis
-nucleus divides into two, each with an identical set of chromosomes
-nuclei are genetically identical
what happens during interphase in mitosis
-period of cell growth, preparing for cell division
-DNA is copied and checked for errors (prevents mutations)
-new organelles and proteins are made
-divided into phases (G1, S, G2)
what happens during prophase
-Chromosomes condense
-The chromosomes consist of two identical chromatids called sister chromatids that are joined together at the centromere
-The two centrosomes move towards opposite poles
-Spindle fibres begin to emerge from the centrosomes
-The nuclear envelope breaks down into small vesicles
-The nucleolus disappears
what happens during metaphase
-Centrosomes reach opposite poles
-Spindle fibres continue to extend from centrosomes
-Chromosomes line up at the equator of the spindle
-Spindle fibres reach the chromosomes and attach to the centromeres
-Each sister chromatid is attached to a spindle fibre originating from opposite poles
what happens during anaphase
-The sister chromatids separate at the centromere
-Spindle fibres begin to shorten
-The separated sister chromatids are pulled to opposite poles by the spindle fibres
what happens during telophase
-Chromosomes arrive at opposite poles and begin to decondense
-Nuclear envelopes begin to reform around each set of chromosomes
-The spindle fibres break down
New nucleoli form within each nucleus
what happens in G1
-cells growing and preparing for mitosis
-organelles duplicate
-transcription
-checks for mutations
what happens in S phase
-chromosomes unwind
-dna is replicated
what happens during G2 phase
cell continues to grow and the new DNA that has been synthesised is checked and any errors are usually repaired
what happens in cytokinesis in plant cells
-vesicles assemble at the metaphase plate
-vesicle fuses with membrane forming 2 cells
what happens in cytokinesis in animal cells
-cleavage furrow forms in the centre of the cell
-cytoskeleton pulls cell surface membrane in until they fuse and form two cells
what is the purpose of mitosis
produces 2 identical daughter cells for:
-cell growth
-cel replacement/tissue growth
-asexual reproduction
how is cell cycle regulated?
-checkpoints where cell signalling proteins ensure damaged cells do not pass to the next stage
what happens at each checkpoint in the cell cycle
-between G1 and S: cell checks for DNA damage
-between G2 and M: cell checks chromosome replication
-metaphase checkpoint: cell checks that that sister chromatids have attached to spindle correctly
