Flashcards in Errors Involving DNA Deck (94)
What are oncogenes?
Genes that increase growth, promotes survival and inhibit apoptosis
Why might oncogenes have an increase in activity?
Due to mutation (either in the gene itself, in other involved signalling proteins or in the transcription factor binding region).
What are tumour suppressing genes?
Genes that inhibit proliferation, reduce growth or promote apoptosis
What is the p53 gene?
A tumour suppressing gene that is commonly mutated
What is slippage in DNA replication?
Where a newly synthesised nucleotide/strand can slip out and so there are extra nucleotides on the strand. Or nucleotides can slip out on the template strand, shortening the DNA strand.
What is mis-match pairing?
When DNA polymerase inserts the wrong nucleotide
How can a mismatch be easily repaired?
There can be a base excision repair from the exonuclease domain of the DNA polymerase.
What results from an increase of p53 activity?
What is DNA replication stress?
Inefficient replication that leads to the replication fork slowing, stalling or breaking
What happens when the replication fork meets a single strand break?
A double strand break occurs
What disease results from a trinucleotide repeat?
What is dysplasia?
Features of abnormal cell growth
Errors in what 4 areas lead to genomic instability?
1. Errors in oncogenes
2. Errors in tumour suppressing genes
3. Errors in chromosome structure
4. Errors in chromosome number
Increasing the activity of which genes results in dysplasia
What is mismatch repair?
When DNA polymerase finds a mistake and so the exonuclease domain cuts out the mistake for polymerase to fix
Outline nucleotide excision repair
A stretch of damaged DNA is removed by endonuclease and replaced by DNA polymerase and joined together by DNA ligase, using a variety of proteins which are produced in the genes controlling this repair
What does UV light do to cells?
It initiates a reaction between 2 thymine molecule to form a pyrimidine dimer.
Why can some DNA synthesis inhibitors be used as antibiotics?
They may only inhibit bacterial DNA synthesis not human
What is non-homologous end joining used to repair
Double stranded breaks
Outline non-homologous end joining
The ends are directly lighted. This is done by proteins binding onto the ends of the breaks, which then recruit other proteins which removed damaged strands and then DNA ligase brings the strands together
What are chromosomal translocations?
When part of a chromosome attaches to another. It can be balanced or unbalanced
What is chromosomal inversion?
When a segment of DNA is reversed end to end.
What type of disease can be caused by translocations
What is a mutation
An alteration in a gene or chromosome
What is a bulky addict
When chemicals bind to areas of DNA and prevent it replicating
When do mutations occur
When DNA repair mechanisms are defective
State exogenous sources of mutation
Ionising radiation, free radical, mutagenic chemicals
What are free radicals
Molecules with an extra electron
State endogenous sources of mutation
DNA replication defects and transposable elements