What does it mean when scientists say that living organisms share a universal genetic code?
How does a universal genetic code relate to the hypotheses about the origin of life on Earth?
How are self-replicating molecules, such as RNA molecules in the “RNA World” hypothesis, essential to the most popular hypotheses about the origin of life on Earth?
How might similarities and differences in genetic codes, or the proteins built as a result of these codes, be used to determine how closely related different species are?

Question

What does it mean when scientists say that living organisms share a universal genetic code?
How does a universal genetic code relate to the hypotheses about the origin of life on Earth?
How are self-replicating molecules, such as RNA molecules in the “RNA World” hypothesis, essential to the most popular hypotheses about the origin of life on Earth?
How might similarities and differences in genetic codes, or the proteins built as a result of these codes, be used to determine how closely related different species are?

anonymous · Answer

All living organisms have a shared ancestor deep in the past, so all living organisms are related to some degree. We might share 99.8% DNA with chimps, but we also share maybe (just a guess, I don't remember the exact number) 24% DNA with lettuce. If all living organisms are related, than their genetic code is universal - one and the same for all organisms.

javk · Answer

Universal genetic code means that a single codon e.g UAA is the stop codon, in all organisms, its not going to mean one thing in humans and something else in plants.