3.7 Mitosis and binary fission Flashcards
What is the difference between mitosis and meiosis in terms of chromosomes
Mitosis produces two daughter cells that have the same number of chromosomes as the parent cell and eachother
Meiosis produces 4 daughter cells, each with half the number of chromosomes as the parent cell
What is mitosis
. The exact division of a cell that results in each of the daughter cells having an exact copy of the DNA of the parent cell
. Genetic make up of the two daughter nuclei is also identical to that of the parent nuclei, assuming there isn’t a mutation.
There are 4 stages
What is interphase and what happens to the DNA
Before the cell divides / mitosis begins
. The DNA is replicated
. The cell expands
. The amount of subcellular structures increase
The two copies of DNA after replication are joined at a place called the centromere
What is the first stage, prophase of mitosis
. The chromosomes condense from being long and thin to short and thick so become visible
. The centrioles (two cylindrical organelles in animal cells) move to opposite poles of the cell, and spindle fibres develop from them which span the cell from pole to pole, and collectively these spindle fibres are called the spindle apparatus
. Nucleolus disappears and the nuclear envelope breaks down so the chromosomes are free in the cytoplasm of the cell
What is metaphase of mitosis (stage 2)
. The chromosomes line up along the equator of the cell
. The chromosomes are seen to be made up of two chromatids, each is an identical copy of DNA from the parent cell
. The chromatids are joined by a centromere, which is connected some microtubules from the poles, so the spindle apparatus makes them line up
What is anaphase of mitosis (stage 3)
Where does the energy for it come from
. The centromere divides into two, and the spindle fibres pull the individual chromatids apart
. The chromatids move rapidly to opposite poles of the cell, and they are now chromosomes
The energy for it comes from mitochondria which gather around the spindle fibres
What would happen if cells were treated with chemicals that destroy the spindle
. The spindle fibres won’t be able to pull the chromosomes to opposite poles so they will stay lined up along the equator
. This means the mitosis stage won’t be able to happen so the cell can’t replicate
What is telophase
. The chromosomes reach their respective poles and become long and thin again before finally disappearing altogether and leaving only widely spread chromatin
. The spindle fibres disintegrate and the nuclear envelope and nucleolus re-form
What is cytokinesis
This is where the cytoplasm divides, leaving two daughter cells
How does cell division work in bacteria
Binary fission
. Circular DNA molecule replicates and both copies attach to the cell membrane
. The plasmids also replicate
. The cell membrane begins to grow between the two DNA molecules and begins to pinch inwards, dividing the cytoplasm into two
. A new cell wall forms between the two molecules of DNA, dividing the original cell into two identical daughter cells, each with their own copy of circular DNA, and a variable number of plasmids
How do viruses replicate since they’re non living
. Viruses are non living so can’t undergo cell division
They replicate by attaching to a host cell with the attachment proteins on their surface
Then they inject their nucleic acid into the host cell
The genetic information on the injected viral nucleic acid then provides instructions for the host cells metabolic processes to start producing the viral components, nucleic acid, enzymes and structural proteins, which are then assembled into new viruses
What is the importance of making copies of parent cells by mitosis
. Growth: All cells that grow from an original cell must be genetically identical
. Repair, if cells are dead or damaged the new ones produced need to be identical.
. Reproduction: Eg single celled organisms dividing by mitosis give genetically identical new organisms
