If you had a protein that developed a mutation that changed its TEMPLATE

Question

strand from 5’AGT 3’ to 5’ATT3’, what amino acid would you expect in the normal protein, and what would you find in the mutant?

Answer 1

To answer this question, you first need to remember the difference between the template and coding strand of DNA. Here is a simple way to remember that:

The template strand is the strand which is used as a template by RNA polymerase to form the RNA (it is what RNA polymerase "reads" and synthesizes the DNA off of. Therefore, the template strand is complementary to the RNA being produced at that location.

The coding strand is the strand which represents (and will be the same as, except T's switched for U's) the codons (the sequence of RNA that directly codes for the amino acid sequence of the protein.

If the template strand was normally 5' AGT 3', then by base pairing rules, the RNA being created off of this template would become 5' UCA 3', which codes for serine (refer to any RNA codon table in a textbook or online). In the 5' ATT 3' mutant, the RNA would become 5' UAA 3', which is a non-amino acid encoding stop codon. This mutation would result in a truncated (shortened) and most likely dysfunctional protein!