Mitosis Flashcards
What is the purpose of mitosis
To produce two genetically identical diploid daughter cells ( having the same number of chromosomes as the parent)
What is interphase
DNA replication occurs here. The two copies of dna after replication remain joined at a place called a centromere
What are the four phases of mitosis called
Prophase metaphase anaphase telophase ( cytokinesis)
What occurs in prophase
The chromosomes become visible initially as thin threads which will alter become shorter and thicker. Animal cells contain centrioles each which move to the poles of the cell. From each of the centrioles spindle fibres will develop which span from pole to pole. The nucleolus disappears and the nuclear envelope disintegrates leaving the chromosomes free in the cytoplasm of the cell
What occurs in metaphase
In metaphase you can see that the chromosomes are made of two chromatids, each chromatid is an identical copy of dna from the parent cell the chromotids are joined by the centromere. It is at the centromere that some microtubles from the poles are attached and the chromosomes are pulled along the spindle apparatus and arrange themselves along the equator of the cell - middle
What occurs in anaphase
In anaphase, the centromeres divide into two and the spindle fibres pull the individual chromatids apart to opposite poles. We refer to them as chromosomes again. The energy for the process is provided by the mitochondria which gather around the spindle fibres. The spindle fibres are shortening short and fat
What occurs in telophase/ cytokinesis
Chromosomes become longer and thinner finally disappearing all together only leaving wide spread chromatin. Spindle fibres disintergrate - the nuclear envelope and nucleolus reform finally cytokinesis the cytoplasm splits and you are left with two identical daughter cells
What occurs in G1
The cell grows physically and in volume of proteins and organelles
What occurs in S phase
DNA replication and much of the cells repair activity
What occurs in G2
DNA has already been replicated but cell increases in size
what is the process of cell division in bacterial cells called
binary fission
describe the process of binary fission
- the circular DNA replicates and both copies attach to the plasma membrane
- the plasmids also replicate
- the cell membrane begins to grow between the two DNA molecules and begins to pinch inwards dividing the cytoplasam in two
- a new cell wall forms between the two molecules of DNA meaning there are two identical daughter cells of the OG parent - eeach with a copy of circular DNA and a variable copy of plasmids
what is the importance of mitosis
growth - when two haploid cells (sperm and an ovum) fuse to form a diploid it needs to undergo mitosis to grow because all the genetic info is there but it needs to grow
- repair - if cells die or are damaged it is important that an identical copy is produced
describe the lytic cycle in viral replication
first the virus uses attachment proteins on its surface to attach to complementary receptor protein on the host, as the virus is acellular and cannot reproduce by itself it uses the host as a mechanism.
the virus injects its DNA or RNA into the host cell
the host cell will then uses its own machinery ( ribosomes) and the nucleic acid to synthesise new viral particles
the host cell will then burst and the viral DNA and replications are released so they can infect further
what is the structure of HIV
they contain nucleic acid as their source of genetic info as DNA OR RNA
- surrounding this is the capsid which is a protein coat layer
reverse transcriptase
- lipid envelope
- attachment proteins
- matrix
