Mitosis and the cell cycle Flashcards
Definition of Chromosome
Linear DNA found in the nucleus.
Definition of Chromatid
Each strand of the DNA
What are the 4 sections in the cell cycle?
Growth/Gap phase 1
Synthesis
Growth/Gap phase 2
Mitosis
What happens in Gap phase 1?
Organelles are copied, normal cellular processes occur, Cell is checked (if mistakes, don’t divide)
What happens in Gap phase 2?
Chromosomes are checked again (if mistakes, don’t divide) similar to gap phase 1.
What happens in Synthesis?
DNA is replicated by DNA polymerase
what happens if a cell is in Gᴼ Phase?
Cell stops dividing/leaves the cell cycle
what is cytokinesis?
Cell division, 1 cell becomes 2 cells
what is mitosis?
Nuclear division, 1 nucleus becomes 2
what are the 5 stages of mitosis?
Interphase, Prophase, Metaphase, Anaphase, Telophase
what happens in interphase?
This is Growth phase 1,2 and synthesis.
Does normal cellular processes, Copies it’s chromosomes, Chromosomes not visible.
what happens in prophase?
Chromosomes condense by coiling, can now be seen with a light microscope, nuclear membrane disappears, spindle fibres form, nucleolus isn’t visible.
What happens during metaphase?
Spindle fibres extend and attach to the centromere of each chromosome. Spindle fibres force the chromosomes to the equator of the cell.
what happens during anaphase?
The centromere that holds the sister chromatids together divides.Spindle fibres contract and pull the sister chromatids to opposite poles of the cell.
what happens during telophase?
the spindle fibres now disappear and a nuclear membrane forms around each set of chromosomes. Chromosomes decondense and the cell begins to divide into 2 (cytokinesis). A nucleolus can now be seen again.
what happens to the nuclear envelope in each stage of mitosis?
Interphase present prophase breaks down metaphase stays broken down anaphase stays broken down telophase reforms
what happens to the chromosomes in each stage of mitosis?
Interphase not visible (copied in s phase) prophase condense, become visible metaphase line up at the equator anaphase chromatids are pulled apart telophase decondense
what happens to the centomeres in each stage of mitosis?
Interphase Holds chromosomes together
prophase Spindle fibres attach towards the end
metaphase Spindle fibres stay attached to them
anaphase Divides
telophase Holds them together again
what happens to the spindle fibres in each stage of mitosis?
Interphase Not present prophase Form and attach towards the end metaphase line up the chromosomes anaphase Shorten to separate chromatids telophase Break down
what happens to the cell membrane in each stage of mitosis?
Interphase Normal prophase Normal metaphase Normal anaphase Normal telophase Pinches in/cleaves so cell can divide (cytokinesis)
what happens to the number of chromosomes at the start compared to the end in mitosis?
it stays the same
mitosis maintains the number of chromosomes
5 things that mitosis is important for
Growth - Animals and plants Repair - to a certain extent Asexual reproduction - mexican hat plant, onions etc Regeneration - starfish, planarian worm Fungi - yeast budding.
what is yeast budding?
Nuclei copied, a bud forms, cytoplasm swells, bud swells more and breaks off, now 2 yeast.
What is checked at the end of G1?
Checks DNA isn’t damaged
What is checked at the end of G2?
Checks all chromosomes have been replicated
What is checked at the end of mitosis?
Checks sister chromatids attached to spindle fibres
What happens if DNA damage is discovered at G2 checkpoint?
The cell cycle is halted and the cell tries to repair the DNA
