Putting It Together: DNA Transcription and Translation

Summary

In this competency you learned the central dogma of biology:

  • DNA is transcribed to RNA via complementary base pairing rules (but with U instead of T in the transcript)
  • The RNA transcript, specifically mRNA, is then translated to an amino acid polypeptide
  • Final folding and modifications of the polypeptide lead to functional proteins that actually do things in cells

Figure 1 shows this:

To make a protein, genetic information encoded by the DNA must be transcribed onto an mRNA molecule. The RNA is then processed by splicing to remove exons and by the addition of a 5' cap and a poly-A tail. A ribosome then reads the sequence on the mRNA, and uses this information to string amino acids into a protein.

Figure 1. Instructions on DNA are transcribed onto messenger RNA. Ribosomes are able to read the genetic information inscribed on a strand of messenger RNA and use this information to string amino acids together into a protein.

Synthesis

This video provides a quick overview of what we’ve just learned:

If something is a central dogma, it’s always true right? Well, biology is about nothing if not exceptions. Arguably ribozymes can be seen as an exception to this central rule. Ribozymes are small catalytic pieces of RNA. In other words, self-sufficient molecules that both carry the directions and carry out the plan. Catalytic RNA molecules are seen as evidence that early life on this planet may not have followed the central dogma of DNA → RNA → protein. Instead, this simpler pathway with a single macromolecule doing all the work may be how life originally evolved. The RNA world hypothesis is the simplest explanation for the origin of life and leads us directly to the next unit!

To learn more, visit Exploring Life’s Origins.