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.
G1 checkpoint- at the end of G1 phase, before entry into S phase. Is cell big enough? Is DNA damaged?
G2 checkpoint- end of G2 phase, start of miotic phase. Did all chromosomes get replicated correctly? Is DNA damaged
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.
Animal cells and cell division.
Cleavage furrow forms around the middle of the cell. The membrane is pulled inwards by the cytoskeleton until it is close enough to fuse.
Plant cells and cell division.
No cleavage furrow can be formed due to cell walls.
Vesicles from the Golgi apparatus fuse with each other and the cell membrane, dividing the cell into 2.
What does meiosis do?
Enables sexual reproduction (increases variation in species), maintains diploid number of chromosomes in specimen.
Crossing over.
Happens in prophase 1 , sections of homologous chromatids are exchanged creating new combinations of alleles.
