Final answer:
To determine the genetic basis for lactase persistence, researchers can analyze the lactase gene from different populations to identify mutations and assess lactase activity associated with these mutations, using CRISPR-Cas9 to establish causality.
Step-by-step explanation:
To design an experiment to determine whether lactase persistence in the different global hot spots was caused by one or several mutations, it is essential to understand the genetic basis of lactase expression first. For a biological experiment akin to the investigations of Francois Jacob and Jacques Monod on gene expression in E. coli, one could utilize similar principles to study lactase persistence. They could collect DNA samples from individuals showing lactase persistence across different geographical locations and sequence the lactase gene (LCT) and its regulatory regions to identify mutations. Comparing these sequences can reveal whether the same mutation appears across different populations or if multiple mutations are leading to lactase persistence.
The next step would involve measuring the activity of the lactase enzyme in these individuals or creating a laboratory model to study the different mutations in vitro. This could be done by inserting the different mutations into cell lines or bacteria that do not naturally express lactase, then assessing the level of lactase activity in the presence of lactose. If mutations from different populations show similar lactase activity, this could suggest a common ancestral mutation. If activity levels differ, it might indicate multiple origins of lactase persistence.
Finally, to confirm that these are indeed the mutations responsible for lactase persistence, researchers could use CRISPR-Cas9 technology to revert the mutations in cells from individuals with lactase persistence to the 'non-persistent' state to see if lactase activity decreases. Conversely, inducing these mutations in non-persistent cells might increase lactase activity, confirming causality.