3.8 The control of gene expression Flashcards
how are cells able to control their metabolic activites
via transcription + translation
define gene mutation
change in base sequence of DNA
can arise spontaneously during DNA replication
define mutagenic agent
increases rate of mutations above naturally occuring rate
ie, ionising radiation, carcinogens, some viruses
base substitution
1 base replaced with another
could be no change due to degenerate nature of genetic code so same amino acid formed
or amino acid change
base addition
1(+) base added to base sequence
frameshift downstream of mutation->amino acid sequence changes
3 bases added- no frameshift
base deletion
1(+)more bases lost from base sequence
frameshift downstream of mutation->amino acid sequence changes
3bases removed= no frameshift
base inversion
sequence of bases seperated from DNA + reinserted backwards at same position
no frameshift
sequence of amino acids inverted in the reinserted region
base duplication
sequence of base inserted 2x/multiple ti,mes
frameshift, downstream of mutation->amino acid sequence
3 bases added->no frameshift->extra amino acids
base translocation
sequences of bases taken out +inserted at diff position
diff amino acid sequence
how do mutations produce a non functional protein/enzyme
- change in DNA base sequence
- change sequence of codons on mRNA
- change in sequence of amino acid in primary structure
- change in position of bonds
- change in tertiary structure + shape of protein + active site
- substrate unable to bind to active site/non-functional protein
define stem cells
unspecialised cells capable of
- self renewal
- specialisation/differentiation
how does stem cell specialisation happen
- stimulus
2. causes selective activation of genes
