Question

Which among the following is the most compelling evidence that all present day cells have common ancestry?

• A. The genes which are absolutely necessary for life have not changed much and are preserved
• B. Life has not originated on earth and has come from some other planet
• C. All proteins are built from the same set of 20 amino acids
• D. All the cells have same type of plasma membrane with exactly similar proteins embedded in them

Answer 1

Answer: (A), (C)

All proteins are built from the same set of 20 amino acids

All proteins found in living systems are mostly made up of only 20 amino acids. If life had multiple origins then there would have been other types of amino acids present in cells of different origins.

Also, most of the genes which code for essential proteins, i.e., the proteins involved in replication of DNA, translation and transcription and also the proteins coding for tRNA are preserved in the organisms. This shows their common ancestry.