The long skinny DNA molecule is in the shape of the famous 'double helix', and we saw how the backbone was quite rigid as we imagined how we walked along it, and saw the 'bases' protruding out to the side and matching up with complementary bases on the other side, giving the appearance of rungs on a ladder.
These 'rungs' however, are not like a ladder – we could not (in our imagination) walk on them because the links between the bases on each side are very weak. This enables the two backbone strands to unwind easily, and then wind up when they are not needed; and this is the very heart of the way DNA works to be the 'code' for all our proteins.
How DNA works – what we know so far
DNA molecules in the nuclei of our cells contain the code for the production of all the proteins that enable us to be alive, and to function. The simplified explanation is that the DNA 'bases' are grouped in a particular order along the DNA chain, and a certain set of these bases is called a 'gene'. Each gene codes for a protein. Hence DNA contains 'the genetic code'. (A group of genes along a substantial length of DNA makes up a chromosome, as described in Part 1).
When it is time for a protein to be made in the cell, for example in order to repair a muscle or to make a digestive hormone, then a complicated dance occurs inside the nucleus and then out in the cell proper (the cytosol or cytoplasm). Chemicals called enzymes (which are themselves special proteins) unwrap a section of DNA containing the particular gene that is needed. Another molecule called ribonucleic acid, or RNA, which is a close cousin of DNA but does not form long helical molecules, now comes into play.
There are many different types of RNA. One of them copies short sections of the code from the long DNA molecule and take it out of the nucleus into the main part of the cell, where, with the help of a different type of RNA called 'transfer-RNA), and a structure called a ribosome (which is built from proteins and yet more RNA) translates this into molecules called 'amino acids', which link together to form a protein. The protein is then wound into its correct shape (shape is very important in biochemical reactions) and is transported by other biological processes and other molecules to the place where it is needed (the muscle or gut, in the examples above).
There are some wonderful explanations, diagrams and animations that show this process – just remember that they are all just models, and none of them are really photographs of what happens, they are products of someone's imaginary super-magnifying spectacles based on interpretation of the results of many experiments. In most of the links below, there is a general assumption about evolution. Rather, in my view all this speaks of an astonishing creator God. You can think of this whatever way you like, it does not detract from the wondrous mechanism of how our cellular mechanisms work to keep us alive.
Alternatively, for a more simplified overview, see www.phschool.com
Some possible advantages in knowing more about how DNA works
We may never understand the fundamental reasons why or how DNA, RNA and proteins interact, but scientists are certainly finding more and more about 'what' happens inside cells. With this knowledge, they can learn to manipulate the chemistry of DNA outside or inside cells to help improve our lives in horticulture, medicine, and even electronics.
Here are three of many examples of how this knowledge is potentially very useful.
Researchers in America have determined how an anti-cancer drug works to help with a rare neurological disease – the medicine acts on the very genetic code within the cell to 'unsilence' a gene that should be turned on, but isn't in the unfortunate patients. (m.ucdmc.ucdavis.edu )
Back home at the University of Queensland, a researcher has found the functional genes in pineapples that control things as ripening time and synthesis of metabolites such as vitamin C. This may lead to more nutritious pineapples being produced in future. (www.uq.edu.au)
And other Australians are continuing the ongoing 100-year-old struggle to breed new wheat varieties that are resistant to diseases such as the fungal 'rusts' that keep outwitting the horticulturalists. CSIRO scientists now have a knowledge of genetics in their armory, and have identified a natural wheat gene that recognises when it is being attacked by the rust fungus and helps mount an attack (yes, plants do have rudimentary immune systems). Knowing this, they can breed resistant strains more efficiently and quicker than they ever could by using trial and error as in the past. (theconversation.com)
Some things we don't yet know
Until recently, scientists were puzzled by the fact that every cell in one organism (for example you) has the same DNA, yet all types of cells are different – a bone cell is not like a muscle cell, which is not like any of the different blood cells, which are not like skin ….. etc. They now know that the protective proteins around the DNA are one way that the cell controls which genes need to be 'turned on' for each cell, and at what time (such as a digestive enzyme is needed when you have had a meal, but not at other times). (www.sciencedaily.com)
There are other controls too, and there are 'start' and 'stop' signals in the code of the DNA itself. There are also sections of DNA that do NOT code for any proteins, and it is slowly being realised these may be involved in controlling which genes do what, for which cells, and at what time, as recently proposed by a team in Sydney (www.sciencedaily.com).
And here is another puzzle. DNA is required to make all the proteins in the cell; yet this cannot happen unless there are proteins (including enzymes) to catalyse the reactions to enable DNA to be de-coded and proteins to be made. This is the proverbial 'chicken and egg' problem – which came first?
The miracle of Life is still not understood by mere humans. But according to the Scripture passage from Corinthians (below), scientists should still persevere with rigorous and ethical investigation and accurate observation, and the willingness to use the information for the good of Mankind, even while realising that our knowledge is 'incomplete'.
1 Corinthians 13:10 "For our knowledge is always incomplete and our prophecy is always incomplete, and when the complete comes, that is the end of the incomplete."
Dr Mark Tronson is a Baptist minister (retired) who served as the Australian cricket team chaplain for 17 years (2000 ret) and established Life After Cricket in 2001. He was recognised by the Olympic Ministry Medal in 2009 presented by Carl Lewis Olympian of the Century. He has written 24 books, and enjoys writing. He is married to Delma, with four adult children and grand-children.
Mark Tronson's archive of articles can be viewed at www.pressserviceinternational.org/mark-tronson.html