Mitosis Flashcards
What is a chromosome
A DNA molecule folded and condensed
Wrapped around a histone protein in eukaryotes.
What forms after DNA replication
2 genetically identical sister chromatids
Where are sister chromatids attatched
At the centromere
Define homologous chromososome
Chromosomes with the same genes but potentially different alleles.
Diploid cells
Cells with homolgous pairs of chromosomes
Diploid is represented by…
2n
Haploid cells
Cells with only one copy of the pair of chromosmes,
Half the number of chromosomes than diploids.
Haploid cells are represented by…
n
What type of cells can’t divide
Specialised and fully differentiated cells
e.g
Red blood cells
What type of cells can divide
unspecialised cells
3 main stages of the cell cycle
Interphase, mitosis and cytokenisis
3 phases of interphase
G1
S
G2
G1 phase of interphase, what happens?
Cell increases in size and new proteins and enzymes are made for DNA replication.
S phase in interphase, what happens?
DNA replicates
G2 phase in interphase, what happens?
Cell gets ready for division, new proteins and organelles are made.
What stage of the cell cycle is where chromomes are not visible?
Interphase
4 Stages of mitosis
Prophase, metaphase, anaphase, telophase
Why is mitosis important
Allows organisms to grow
Allows organisms to replace cells in order to repair tissues
Results in genetically identical cells
Asexual reproduction in some organisms (not prokaryotes)
What happens in prophase
Nuclear membrane breaks down
Centrioles move to the poles of the cell and make spindle fibres.
chromosomes condense and become visible.
What happens in metaphase
Spindle fibres which attach to the centromere of each chromsome
Chromosomes align down the equtor of the cell.
What happens in anaphase
Spindle fibres contract, dividing the centromere.
Sister chromatids are pulled apart to opposite poles pf the cell ( the chromatids appear as V shapes)
What happens in telophase
Chromsomes reach the poles and the spindle fibres break down.
New nuclear membrane forms around the group of chromsomes
Chromosomes uncondense and begin to form chromatin again.
What happens in cytokenisis
The cytoplasm divides; producing two genetically identical daughter cells
Cell division in cancer
Uncontrolled cell division leading to tumours
Cancer cells
Divide uncontrollably
Have a shorter cell cycle and divide more often.
How are cancer cells dangerous
Unspecialised and have no function so they cause harm by damaging organs or blocking blood vessels to organs.
What parts of the cell cycle to cancer treatments disrupt
DNA replication (interphase)
Spindle formation/contraction (prevents anaphase)
Cytokenisis
Why do cancer treatments kill more cancer cells than healthy cells
Tumour cells divide more frequently than normal cells s the treatments target tumour cells more.
