DNA repair Flashcards
what do cancer cells display
altered behaviour
what is the system by which cells become cancerous?
normal cells become activated by oncogenes into pre-cancerous cells, which then lose rumour suppressor function and turn into benign neoplasia, then cell functions become altered and they become malignant neoplasia cancerous cells
what is neoplasia
tissue composed of cells with the ability to grow beyond their normal confines
what does tumorigenesis require
alterations in cell function
define hyperplasia
too many cells
define dysplasia
abnormal looking cells
define adenoma
a benign tumour
define carcinoma
a malignant tumour
what are the mutations involved in cancer development
initiating mutation - first clonal expansion, second mutation - second clonal expansion, third mutation - third clonal expansion and fourth mutation - fourth clonal expansion
etc.
explain what tumour elevation is and what it does to populations of cells
tumour elevation is not linear but is dynamic and gives rise to populations of cells with distinct proliferative advantage
what does oncogene activation result in?
precancerous state which can be accompanied by increased DNA damage
how are pre-cancerous states kept under control
by checkpoints
these prevent proliferation of these cells
what does loss of tumour suppressor function (linked to failure of cell cycle checkpoints) enable
pre-cancerous cells to proliferate
how do proliferating tumour cells evolve
through mutagenesis and acquire altered cell function
what do tumour cells often exhibit changes in?
chromosome number and structure
define mutations
- a change in the structure of a nucleotide sequence, often, in a gene
- the altered sequence or gene resulting from such a change
- a change in the karyotype (chromosomal mutation)
how does UV (sunburn) cause cancer
2 adjacent nucleotides become linked
how can be bases be lost
due to attack by water molecules (depurination/depyrimidination) leaving a non-coding lesion
these non-coding lesions result in coding changes after DNA replication
what can deamination of different bases lead to
the generation of non-coding bases that cannot pair with normal bases during replication.
what does energy production in mitochondria produce
highly reactive oxygen species (ROS)
what can ROS cause
DNA breaks and oxidised bases
what does oxidation of guanine to 8-oxo dG cause
mispairing during replication and therefore to genetic change
what does methylation of bases cause
mispairing of bases during replication leading to genetic change
what is 5-me cytosine
a normal tolerated form of methylation that plays a role in gene regulation during transcription
