Scientists have found that the lifetimes of mRNAs coding for pair-rule regulatory elements in Drosophila embryos may last only a few minutes. What does this suggest about the overall developmental plan of an animal body?

This phenomena suggests that building an animal body will require a lot of precisely timed steps (building an animal body will involve a lot of steps, precision, and timings).

Explanation:

Scientists have discovered that the lifetimes of mRNAs( Ribonucleic acids) coding for pair-rule regulatory elements in Drosophila embryos may last only a few minutes. This discovery is telling us that if you go into the process of building an animal body, such process will involve a lot of timings and precision.

However, this is a very tedious task as it involves a lot of precision and timings. For you to accomplish such task you must not miss any step, also all the steps must be precisely timed.

Therefore, the discovery insinuates that building an animal body requires a sequence of steps which must be precisely timed.

your answer is "the 1950's"