The last common ancestor of modern organisms must have used
A)D amino acids.
B)L amino acids.
C)both D and L amino acids.
D)either D or L amino acids.

Question

Quizplus · Accepted Answer

All modern organisms use L-amino acids to make proteins. While some organisms (such as bacteria) can use D-amino acids for other functions, there is no evidence that the last common ancestor used D-amino acids for protein synthesis. Therefore, the best choice is B.

The Last Common Ancestor of Modern Organisms Must Have Used