Once the DNA sequence of a new gene is known, how do scientists figure out the function of its protein product?
One of the first things a scientist would do is use the Universal Genetic Code to predict the amino acids encoded by the gene. Unfortunately, this only gives a list of the protein's sequence. Proteins actually don't remain in the nice long, straight lines they're coded in: they fold, and this folding is the key to their unique functions.
Proteins fold into a variety of 3-dimensional shapes. Experiments to unfold and refold proteins have shown that the amino acid sequence itself contains all the instructions needed for proper folding. Scientists have searched for rules governing folding but have found no reliable way to predict a 3-dimensional structure from a simple sequence.
Knowing a protein's sequence does help, however. Having determined the sequence, the next thing a scientist would do is compare the DNA sequence of the newly discovered gene with those of all previously discovered genes. Perhaps the sequence of the new gene will be similar to another whose function is already known. Scientists have already determined the functions of many proteins using a variety of methods.
For example, they can determine:
All of this information tells a scientist something about the possible functions of a protein. With this knowledge, the scientist can formulate testable hypotheses about the protein's role.
If you can relate the sequence of a new protein to that of one that has already been characterized using tests like these, you have a jump on figuring out what the new protein might be doing in the cell. What sorts of similarities might a scientist find between a newly discovered gene and one we know more about?
If the new gene shares no similarities with any other known gene, the scientist will term it "unique." Without any clues to go on, it is more difficult to propose and test hypotheses about the gene's function, but previous research findings can be useful.
Background information about a wide variety of known proteins helps speed the study of new ones. In the same way, basic research -- meaning research for the purpose of discovering any and all information, not necessarily immediately useful information -- is crucial to the progress of all science.
Funding provided by a Howard Hughes Medical Institute Precollege Science Education Initiative for Biomedical Research Institutions Award (Grants 51000125, 51000176)
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