lecture 1 Flashcards
in which polarity does DNA run in?
5’-3’
in which are the genes expressed: chromatin & heterochromatin?
genes expressed only in chromatin
what is the structure of human Hb?
a2b2; a chain 141 aa long, coded for by HBA1 gene
b chain 146 aa long, coded for by HBB gene
give examples of small scale mutations
- base substitutions
- base deletions
- base additions
what are large scale mutations?
- chromosome rearrangements
- transposable element insertion
what is a transition?
a single nucleotide change in which a base is converted to the same type of base (e.g. purine -> purine)
what is a transversion?
a single nucleotide change in which a base is converted to a different type of base (e.g. purine -> pyrimidine)
what is sickle cell anaemia caused by?
biochemical effects = Hb precipitates in low O2
caused by base substitution in codon 7 of HBB
this causes 6th aa to be changed from glutamate -> valine
mutations alter amount of gene product by…
- altering promoter activity
- altering translation initiation at AUG
- preventing mRNA splicing
- reducing mRNA stability
mutations change polypeptide length by…
- deletions or additions
- chain termination mutations
- frameshift mutations
what is a chain termination/non-sense mutation?
changes sense codon into a stop codon
what is meant by transposable element insertion?
movement of discrete DNA elements, inactivating gene
what is a key feature of transposable elements?
they are supernumerary; contained in excess of required amount
what does excision of transposable elements result in?
activation of gene
what are insertion sequences?
the simplest form of transposable element
