chapter 4: the cell cycle Flashcards
what is binary fission?
the method of cell reproduction/replication of prokaryotes. it is a form of asexual reproduction
first step of binary fission
- replication
- the coiled chromosome uncoils and duplicates
- plasmids duplicate
- any other structures such as ribosomes duplicate
second step of binary fission
elongation
- the cell grows long enough to divide in to two separate cells
third step of binary fission
separation
- also called cytokinesis
- the chromosomes move away from each other
- the cell pinches into 2
- creates a new cell wall (if applicable) called the septum and membrane
how is variation found in binary fission?
through mutation
how do you figure out the how many daughter cells there will be once after time?
Number of divisions = time / how long it takes for a division
2 to the power of no. of divisions
what is the cell cycle?
the eukaryotic cell cycle is the replication of eukaryotic cells
what are the phases of the cell cycle?
interphase, mitosis and cytokinesis
what is phase one of interphase?
G1 phase is when the cell gets bigger by increasing the amount of cytosol. it makes copies of its organelles, and makes molecules (such as protein) it will need later on.
what is phase 2 of interphase?
the S phase - DNA replicates, turning the chromosome into 2 identical sister chromatids. if they are held together by a centromere, they are sill considered a chromosome.
what is phase 3 of interphase?
G2 phase - increases in cytosol more as well synthesis more proteins in preparation for mitosis
what is mitosis?
Mitosis - occurs once the DNA replication is complete and the cells have passed all checkpoints. Mitosis has 4 stages, Prophase, Metaphase, Anaphase and Telophase.
what is prophase?
prophase - the nuclear envelope breaks down, DNA as chromatins condenses into chromosomes, and spindles form
PECS
what is metaphase?
metaphase - the chromosomes position on the equator of the cell, microtubules bind to the sister chromatids, and the spindles extend from the centriols
what is anaphase?
anaphase - separation of sister chromatids and spindles shorten to pull them to the poles of the cell
what is telophase?
telophase - uncoiling of chromosomes, nuclear envelope reforms and the spindles disappear
what is cytokinesis?
the final stage of the cell cycle where the cell separates. a nucleus forms on each side of the cell, cytosol and other organelles surround the nucleus.
cytokinesis in animals
The cell membrane either furrows and then splits
cytokinesis in plants
cellulose is deposited into a cell plate and then it separates.
what is the G1 checkpoint?
occurs right after the G1 phase.
- grown to the right size
- has synthesised enough protein for DNA replication
- checks if DNA has been damaged
- enough oxygen and nutrients
it looks at is if the environment is favourable to keep going.
what is the G2 checkpoint?
ensures that DNA has replicated properly in the S phase, and that the cell has enough resources for mitosis.
what is the metaphase checkpoint (spindle assembly)?
In the metaphase checkpoint, the cell checks the formation of the spindle fibres. If the chromosomes are lined up in the correct location, the cell proceeds to anaphase.
what happens if a cell fails a checkpoint?
goes into apoptosis
what is apoptosis?
regulated/programmed cell death. if it malfunctions there may be deviant cell behaviour.
- helps maintain cell numbers
- defence against damaged/dangerous cells
