Cell division, diversity and organisation Flashcards
Cell division
-eukaryotic cells enter the cell cycle and divide by either mitosis or meiosis
-prokaryotic cells replicate through binary fission
- viruses do not undergo cell division as they are non living
What are the 3 stages of the cell cycle?
-Interphase(G1, s and G2)
-nuclear division(mitosis or meiosis)
-cytokinesis
Interphase
-longest stage in the cell cycle
Interphase :G1
-protein synthesis occurs to make proteins involved in synthesising organelles
-organelles replicate
-cell is checked that it is the correct size, has the correct nutrients, growth factors and that there is no damaged DNA.
-if cell does not pass these checks, replication will not continue
Interphase: s
-DNA is replicated
Interphase: G2
-cell continues to grow, energy stores increase and the newly replicated DNA is checked for copying errors
What are checkpoints?
-monitor and verify if each process of the cell cycle have been accurately completed.
G1 checkpoint
-end of the G1 phase, before entry into the S phase
-if cell does not satisfy requirements it will enter G0(Resting phase)
G2 checkpoint
-end of the G2 phase, before the start of the mitotic phase. cell needs to check if DNA has been replicated without errors
Mitosis
-created 2 identical diploid cells
-used for growth, tissue repair and asexual reproduction in plants, animal and fungi.
What are the 4 stages of mitosis
-prophase
-metaphase
-anaphase
-telophase
PMAT
Prophase in mitosis
-chromosomes condense and become visible
-in animals, the centrioles separate and move to opposite poles of the cell
-centrioles create spindle fibres which are released from both poles to create a spindle apparatus which will later attach to the centromere and chromatids on the chromosome
-plants have a spindle apparatus but lack centrioles
-nuclear envelope disintegrates and nucleus fades away
Metaphase in mitosis
-chromosomes align along the equator of the cell(metaphase plate)
-spindle fibres are released from the centrioles and attach to the centromere and the chromatids
-spindle assembly checkpoint occurs in this stage( it ensures every chromosome has attached to a spindle fibre before anaphase)
Anaphase in mitosis
-spindle fibres begin to shorten and move towards the centrioles and pull the centromere and chromatids they are bound to towards the opposite poles
-centromere divides and the individual chromatids are pulled to each opposite pole
-stage requires energy in the form of ATP which is provided by respiration in the mitochondria
Telophase in mitosis
-chromosomes are now at each pole of the cell and become longer and thinner again
-spindle fibres disintegrate and the nuclear membrane reforms
-the nucleolus also forms