Cell Division Flashcards
Interphase.
G1- growth phase. Organelles replicate and cell increases in size.
S- synthesis phase. DNA is replicated.
G2- second growth phase. Cell continues to increase in size and energy stores increase.
Miotic stage.
Mitosis- nucleus divides.
Cytokinesis- cytoplasm divides and 2 cells are produced.
G0.
Cells leave the cycle temporarily or permanently. Due to, differentiation, DNA of the cell may be damaged, ageing increases number of cells.
Checkpoints.
Key to make sure that the cell cycle is okay to continue.
G1 - checks that the cell has all the chemicals needed for replication are present and checks for any damage to DNA before entering S phase.
S phase - cell replicates it’s DNA, ready to divide by mitosis.
G2 checkpoint - the cell checks whether all the DNA has been replicated without any damage if it has then the cell can enter mitosis.
Spindle assembly checkpoint- point in mitosis where all the chromosomes should be attached to spindle fibres and aligned.
Importance of mitosis.
Growth and repair.
Asexual reproduction.
Chromosomes.
Before mitosis all DNA is replicated. Each DNA molecule is converted to into 2 identical molecules (chromatids)
2 chromatids are joined at a region called the centromere.
Stages of mitosis.
Prophase.
Metaphase.
Anaphase.
Telophase.
Cytokinesis.
Prophase.
Chromatin fibres coil and condense to make chromosomes.
Nuclear membrane begins to break down.
Protein microtubules create spindle fibres.
Centrioles migrates to opposite ends of the cell.
Nuclear envelopes disappear.
Anaphase.
Centromeres divide. Chromatids are separated and pulled to opposite ends of the cell by spindle fibres.
Telophase.
Chromatids reach the poles of the cell, they are now called chromosomes.
Nuclear enveloped reform.
Chromosomes start to uncoil.
Nucleolus forms.
Cytokinesis.
Division of cell into 2 separated cells.
