CELLS 2 (specialisation, mitosis, cell cycle & cancer) Flashcards
what are the two genes called that control cell division?
tumour supressor gene and proto-oncogenes
what does the tumour suppressor gene do in cell division?
reduce division by promoting apoptosis
what does the proto-oncogenes do in cell division?
increase cell division by promoting the cell cycle
what is apoptosis in terms of the tumour suppressor gene?
when cells self destruct in order to reduce rate of division
what is the role of the 2 genes that control the cell cycle?
- cells divide at a constant rate
- dead or worn out cells are replicated
what happens if the tumour suppressor or porto-oncogene is mutated?
tumours can form
what are the two types of tumours?
Benign (non cancerous) & malignant (cancerous)
cause of cancer
damaged or mutated tumour suppressor or proto-oncogene leading to uncontrolled cellular division = tumours
What is the difference between a malignant and benign tumour?
M : cancerous & form secondary tumours via the blood system in metastasis
B: non-cancerous & don’t invade neighbouring tissues ( no metastasis )
what’s one way that a benign tumour can be harmful?
They can cause blockages which can increase the pressures on certain organs
how does chemotherapy work?
- prevents the DNA from cancer cells from replicating
- inhibits metaphase (chromosomes lining up) by interfering with spindle formation
What are the three stages called during interphase?
Growth 1, Synthesis and Growth 2
what happens during G1 phase in interphase?
- cell grows
- proteins are made by the cell eg RNA + protein
what happens during Synthesis (S) phase in interphase?
the DNA replicates so each chromosome has an identical sister chromatid
what is a chromatid?
half of a chromosome (eg one arm)
-individual strand of dna
define chromosome
long DNA molecule, made of nucleic acids in form of 2 identical sister chromatids
what happens during G2 phase in interphase?
- cell grows bigger
- newly synthesised DNA is checked for error
- DNA is repaired
- biosynthesis ( organelles replicated )
what is the order of the 4 stages in mitosis?
P-M-A-T
prophase, metaphase, anaphase, telephase
what happens in cytokinesis?
the cell membrane and cytoplasm divide to form 2 identical daughter cells
what happens during prophase?
- chromosomes are free in cytoplasm
- nucleolus breaks down and disappears
- spindle fibres begin to form from centrioles
what is the nucleolus? & when is it broken down
section in nucleus (very centre) that produces ribosomes
- broken down during prophase
what happens during metaphase?
- the chromosomes align along the equator
- spindle fibres formed by microtubules from the centrioles.
what are the spindle fibres made of in a cell?
made of microtubules
what happens during anaphase?
- centrometres divide
- individual chromatids pulled apart to opposing poles
what is a centrometre
what holds the two sister chromatids together in a chromosome.
what happens during telophase
- the nuclear envelope reforms
- the spindle disintegrates
- chromosome longer and thinner
how do prokaryotic cells divide?
binary fission
describe 4 stages in binary fission
- plasmid & nucleoid (circular dna) replicated
- cell grows
- dna opposite poles
- cytokinesis and formation of new cell wall made of peptidoglycan
= 2 daughters cells
what are 2 things that might happen to a cell when it becomes specialised?
Change shape + contents (eg. amount of organelles)
define differentiation
when a cell becomes specialised for a particular function.
which eukaryotic organelle in breaks down and hydrolyses foreign matter
lysosomes
mitotic index calculation formula
number of cells with condensed chromosomes ( dividing) / total no. cells x 100
how can you tell if a cell is dividing under a microscope
if the chromosomes are visible
what’s is a mitotic cell?
a cell that replicates to replace damaged cells
why take a cell sample from a root or shoot tip?
Cells are actively growing so the cells will be undergoing mitosis .
benefits of binary fission
more efficient, less energy needed
negatives of binary fission
mutations are inherited, reduced variation, all die in unfavourable conditions
