Mutations and Their Effect on Proteins
A change to one base may change one amino acid, and a changed amino acid may change the shape the protein folds into. Explains why most mutations do nothing while a few change everything.
What a learner can do afterwards
- Works out what a given single base change does to the amino acid sequence.
- Explains why a mutation in an enzyme's active site matters more than one further along the chain.
- Gives a reason why most mutations have no visible effect at all.
1 · Read
A mutation is a random change in DNA. A substitution swaps one base: sometimes nothing changes, sometimes one amino acid changes, sometimes a stop appears early. Insertions and deletions are more serious because they shift the whole reading frame and scramble every triplet downstream.
A changed amino acid can change the shape the protein folds into, and shape decides the job. A change inside an enzyme active site matters most, since the target no longer fits. Yet most mutations do nothing, because many land in silent stretches or swap in the same acid.
Use this mini table: CAA and CAG both mean glutamine, while UAA means stop. Changing CAA to CAG is silent, since the acid stays glutamine. Changing CAA to UAA is severe, since the chain stops early and the enzyme never forms its active site.
Trace every mutation in order: name the type, find the new acid, judge the shape. Repair enzymes fix most slips, and mutagens such as UV and smoke raise the error rate, so errors that survive proofreading are rare.
Trace the base change to the acid change to the shape change to judge it.
2 · Watch
Take it off screen
Where it sits
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.