• Question: Is it possible that organelles and proteins have actually "changed" over time due to genetic mutations being inherited from offspring, causing organelles and proteins to be constructed of different amino acids than they originally have been, yet, working the same, unaffected by the change?

    Asked by dearlydie to Jo, Loren, Sam, Toby on 25 Jun 2014.
    • Photo: Tobias Warnecke

      Tobias Warnecke answered on 25 Jun 2014:

      Hi dearlydie,

      yes, you’re right. And this happens all the time through evolution. Some amino acids are very hard to replace for the function of the protein, so if a mutation happens at that particular site in the DNA, the protein stops functioning. But many mutations are what we call “neutral”, so even if you suddenly have a different amino acid in the protein, the protein functions just fine. So over time, these mutations get passed on and proteins become more dissimilar in their amino acid sequence, but they keep doing the same job. It’s quite odd, really. Some proteins, when you compare the amino acid sequence, look very different (say, only 20% of amino acids are the same), but they turn out to fold into the same 3D structure and do the same thing – quite remarkable really.

    • Photo: Jo Nettleship

      Jo Nettleship answered on 25 Jun 2014:

      Hi dearlydie,
      Yes, proteins change over time due to evolution. sometimes the DNA is mutated because the cells make an error and this mutation is carried though evolution. In many cases the change makes no difference to the function of the protein, however sometimes this change can cause a disease. It is actually this system of mutation which gives rise to evolution itself. Without changes in DNA different animals would not have evolved.
      Interestingly some of these DNA changes are due to viruses. When a virus infects a human say, it inserts its DNA into the humans. If viral DNA actually has a benefit, then evolution keeps it there. If you compare DNA from different viruses and organisms you can see comparisons, and sometimes the species you are looking at are not close together in the phylogenetic tree (or tree of life).

    • Photo: Loren Macdonald

      Loren Macdonald answered on 26 Jun 2014:

      Hi Dearlydie,

      Yes, if we line up the ‘code’ to the same proteins across different organisms, you can see changes and these can be used to map evolution. Say, everything from a certain point has a certain change to the protein that changes it slightly to adapt better to something- then this carries on through generations.

      However, there are also changes to the amino acid makeup that might not affect the actual protein structure that may have been passed on just because of chance. Usually, you would assume, when a mutation happens and becomes dominant in a population, it is because it is beneficial to the organism and probably changes the protein for the better. However, when we do alignments of the same proteins, as I said, they often have many different amino acids changed (usually the important parts, however, remain the same- like the active site or something).