lecture 1 Flashcards
(21 cards)
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
what are composite transposons?
a core region flanked by insertion sequences
what are non-composite transposons?
central region not flanked by insertion sequences
what are the different ways transposable elements can cause mutation?
- insertion into genes
- insertion into regulatory sequences, causing change in gene expression
- chromosomal variation
what is a missense mutation?
a change to the DNA causing a different amino acid to be inserted into the polypeptide
what is a neutral mutation?
changes an amino acid into another with similar properties
what is a silent mutation?
when a change to the codon does not alter the amino acid coded for
