session 9-mutagenesis Flashcards
(26 cards)
Base substitutions can be transitional or transverse. What is the difference?
transitional=purine to purine OR pyrimidine to pyrimidine
transverse=purine to pyrimidine OR pyrimidine to purine
Even if a point mutation is in non coding region, what else can be affected?
splice sites, promoter sequence and binding sites
what does insertion/deletion of a single nucleotide (single base mutation) , a few nucleotides (triplets) or millions of nucleotides (tandem duplications) cause?
frameshift mutation
what is a missense mutation?
a mutation in which one amino acid replaces another
what is a nonsense mutation?
amino acid changes to stop codon
what induces mutations?
chemicals and radiation
chemicals that cause mutations are called…
mutagens
what is a wild type trait?
trait that is most common within that population
how does mismatch repair work?
enzyme detects incorrect pairing and excises and replaces it. Termed as ‘proofreading’
how does excision repair work?
- damaged DNA is removed and replaced using dna polymerase
- Nucleotide excision-repairs up to 30 bases (repairs UV damage and carcinogens)
- base excision-replaces 5 bases max (repairs oxidative damage)
what does the ‘guardian of the genome’ do and what is its actual name?
protein p53-if DNA damage is too severe and cannot be fixed..apoptosis is promoted
what are oncogenes?
a gene which can transform a cell into a tumour cell
what is a proto oncogene?
normal gene that can promote cell division or apoptosis. If mutates, it can become an oncogene and contribute to cancer
when is southern blotting valuable?
when analysis of larger segments of DNA within and around gene is necessary
-also used to analyse triplet repeat disorder
what is the general role of array comparative genomic hybridisation (Array CGH)?
compare patients DNA against normal control DNA to see if there are any chromosomal changes
A point mutation can be 1 of 3 types of mutation. what are the 3 types?
- silent
- missense
- nonsense
What is a silent mutation?
Single base substitution which does not substitute amino acid
Note:some can disrupt RNA splicing and cause heritable diseases, still.
What do gains or losses of base pairs create, when they produce a frameshift?
Ptc-premature termination codons
What happens to mRNAs that contain PTCs?
Degrades by nmd (nonsense mediated decay) and little or no protein is produced
What is tautomeric shift?
Four bases-proton briefly changes position-behave as altered template base during DNA replication
In tautomeric form, what base pairs with what?
C with A
T with G
What is IQ
Aromatic amine food mutagen-found in cooked meats and cigarette smoke
Disrupts packing of DNA
What do UV light photons do to DNA bases?
Causes advance thymine a to join with one another-resolve spontaneously though through photoreactivation
When are the human genes that encode mismatch repair enzymes commonly mutated?
Cases of hereditary non polyps is colorectal cancer
