At the molecular level, gene duplication often produces novelty in a lineage. This process provides another evolutionary pathway by which a protein can switch functions, without loss of the original function. What analytical approach helped the most to answer the question of evolution in the aldosterone–M receptor pair in the study of Jamie Bridgham and her colleagues?
1. analysis of fossil records
2. analysis of receptors in human
3. phylogenetic study
4. forward mutation