After three half-lives, a sample contains 10 grams of parent isotopes. how many grams of the parent isotope were present to start?

The answer is actually (80). 80/2 is 40, 40/2 is 20, and 20/2 is 10, thus the answer is 80.

this protocol provides a detailed procedure for co-immunoprecipitation (co-ip) to identify protein–protein interactions.

c. heat from the poles back down towards the equator.