Consider the following DNA sequence: 3' -- -- 5'
Its mRNA transcript will be:
5' -- -- 3
The resulting polypeptide will be:
(START) THR-GLY-ASN-VAL-CYS-TYR-ARG-GLN-VAL -MET-VAL (STOP)
POINT MUTATIONS are errors in DNA replication in which only on nucleotide base pair is
changed, there are different categories of point mutations:
Silent Mutations - changing the base pair doesn't affect the amino acid sequence of
the polypeptide. For example, in the above DNA sequence, what happens when you
substitute a G for the marked A in the triplet TTA?
mRNA codon:
Amino acid:
Overall effect:
Missense Mutations - changing the base pair affects the amino acid sequence of the
polypeptide, possibly with direct, traceable effects in the individual. For example, in
the above DNA sequence, what happens when you substitute an A for the marked T
in the triplet GTT?
mRNA codon:
Amino acid:
Overall effect:
CHAIN TERMINATION MUTATIONS - changing the base pair creates a stop codon
where there shouldn't be one. For example, in the above DNA sequence, what
happens when you substitute a T for the marked G in the triplet ACG?
mRNA codon:
Amino acid:
Overall effect: