Francis Crick Quotations

It would appear that the number of nonsense triplets is rather low, since we only occasionally come across them. However this conclusion is less secure than our other deductions about the general nature of the genetic code.

The balance of evidence both from the cell-free system and from the study of mutation, suggests that this does not occur at random, and that triplets coding the same amino acid may well be rather similar.

The meaning of this observation is unclear, but it raises the unfortunate possibility of ambiguous triplets; that is, triplets which may code more than one amino acid. However one would certainly expect such triplets to be in a minority.

A comparison between the triplets tentatively deduced by these methods with the changes in amino acid sequence produced by mutation shows a fair measure of agreement.

It is one of the more striking generalizations of biochemistry - which surprisingly is hardly ever mentioned in the biochemical textbooks - that the twenty amino acids and the four bases, are, with minor reservations, the same throughout Nature.

It seems likely that most if not all the genetic information in any organism is carried by nucleic acid - usually by DNA, although certain small viruses use RNA as their genetic material.

Moreover the incorporation requires the same components needed for protein synthesis, and is inhibited by the same inhibitors. Thus the system is most unlikely to be a complete artefact and is very probably closely related to genuine protein synthesis.

If poly A is added to poly U, to form a double or triple helix, the combination is inactive.

Attempts have been made from a study of the changes produced by mutation to obtain the relative order of the bases within various triplets, but my own view is that these are premature until there is more extensive and more reliable data on the composition of the triplets.

This seems highly likely, especially as it has been shown that in several systems mutations affecting the same amino acid are extremely near together on the genetic map.

A final proof of our ideas can only be obtained by detailed studies on the alterations produced in the amino acid sequence of a protein by mutations of the type discussed here.

If, for example, all the codons are triplets, then in addition to the correct reading of the message, there are two incorrect readings which we shall obtain if we do not start the grouping into sets of three at the right place.

It has yet to be shown by direct biochemical methods, as opposed to the indirect genetic evidence mentioned earlier, that the code is indeed a triplet code.

It now seems certain that the amino acid sequence of any protein is determined by the sequence of bases in some region of a particular nucleic acid molecule.

Do codons overlap? In other words, as we read along the genetic message do we find a base which is a member of two or more codons? It now seems fairly certain that codons do not overlap.

How is the base sequence, divided into codons? There is nothing in the backbone of the nucleic acid, which is perfectly regular, to show us how to group the bases into codons.

If the code does indeed have some logical foundation then it is legitimate to consider all the evidence, both good and bad, in any attempt to deduce it.

It now seems very likely that many of the 64 triplets, possibly most of them, may code one amino acid or another, and that in general several distinct triplets may code one amino acid.

Unfortunately it makes the unambiguous determination of triplets by these methods much more difficult than would be the case if there were only one triplet for each amino acid.

It seems virtually certain that a single chain of RNA can act as messenger RNA, since poly U is a single chain without secondary structure.

By using polymers of different composition and assuming a triplet code one can deduce limited information about the composition of certain triplets.

While Occam's razor is a useful tool in the physical sciences, it can be a very dangerous implement in biology. It is thus very rash to use simplicity and elegance as a guide in biological research.

Jim and I hit it off immediately, partly because our interests were astonishingly similar and partly, I suspect, because a certain youthful arrogance, a ruthlessness, an impatience with sloppy thinking can naturally to both of us.

For simplicity one can think of the + class as having one extra base at some point or other in the genetic message and the - class as having one too few.

Again the message to experimentalists is: Be sensible but don't be impressed too much by negative arguments. If at all possible, try it and see what turns up. Theorists almost always dislike this sort of approach.

Finally one should add that in spite of the great complexity of protein synthesis and in spite of the considerable technical difficulties in synthesizing polynucleotides with defined sequences it is not unreasonable to hope that all these points will be clarified in the near future, and that the genetic code will be completely established on a sound experimental basis within a few years.

Christianity may be OK between consenting adults in private but should not be taught to young children.

Evolution is cleverer than you are.

Biologists must constantly keep in mind that what they see was not designed, but rather evolved.

To produce a really good biological theory one must try to see through the clutter produced by evolution to the basic mechanisms lying beneath them, realizing that they are likely to be overlaid by other, secondary mechanisms. What seems to physicists to be a hopelessly complicated process may have been what nature found simplest, because nature could only build on what was already there.

When you start in science, you are brainwashed into believing how careful you must be, and how difficult it is to discover things. There's something that might be called the 'graduate student syndrome'; graduate students hardly believe they can make a discovery.

The major credit I think Jim and I deserve ... is for selecting the right problem and sticking to it. It's true that by blundering about we stumbled on gold, but the fact remains that we were looking for gold. Both of us had decided, quite independently of each other, that the central problem in molecular biology was the chemical structure of the gene. ... We could not see what the answer was, but we considered it so important that we were determined to think about it long and hard, from any relevant point of view.

What could be more foolish than to base one's entire view of life on ideas that, however plausible at the time, now appear to be quite erroneous? And what would be more important than to find our true place in the universe by removing one by one these unfortunate vestiges of earlier beliefs?

Consciousness is somehow a by-product of the simultaneous, high frequency firing of neurons in different parts of the brain. It's the meshing of these frequencies that generates consciousness, just as tones from individual instruments produce the rich, complex, & seamless sounds of a symphony orchestra

If you want to understand function, study structure,

Anybody who believes that the earth is less than 10,000 years old needs psychiatric help.

A man who is right every time is not likely to do very much.

Chance is the only source of true novelty.

Protein synthesis is a central problem for the whole of biology, and that it is in all probability closely related to gene action.

We are sometimes asked what the result would be if we put four +'s in one gene. To answer this my colleagues have recently put together not merely four but six +'s.

Almost all aspects of life are engineered at the molecular level, and without understanding molecules we can only have a very sketchy understanding of life itself.

Trying to determine the structure of a protein by UV spectroscopy was like trying to determine the structure of a piano by listening to the sound it made while being dropped down a flight of stairs.

It is notoriously difficult to define the word living.

I think she [Rosalind Franklin] was a good experimentalist but certainly not of the first rank. She was simply not in the same class as Eigen or Bragg or Pauling, nor was she as good as Dorothy Hodgkin. She did not even select DNA to study. It was given to her. Her theoretical crystallography was very average.

Exact knowledge is the enemy of vitalism.

Our ... advantage was that we had evolved unstated but fruitful methods of collaboration ... If either of us suggested a new idea, the other, while taking it seriously, would attempt to demolish it in a candid but non-hostile manner.

You can do reverse engineering, but you can’t do reverse hacking.

It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.

A knowledge of the true age of the Earth and of the fossil record makes it impossible for any balanced intellect to believe in the literal truth of every part of the Bible in the way that fundamentalists do.

Exploratory research is really like working in a fog. You don't know where you're going. You're just groping. Then people learn about it afterwards and think how straightforward it was.

In my experience most mathematicians are intellectually lazy and especially dislike reading experimental papers. He seemed to have very strong biological intuitions but unfortunately of negative sign.

Rather than believe that Watson and Crick made the DNA structure, I would rather stress that the structure made Watson and Crick.

I also suspect that many workers in this field [molecular biology] and related fields have been strongly motivated by the desire, rarely actually expressed, to refute vitalism.

One can say, looking at the papers in this symposium, that the elucidation of the genetic code is indeed a great achievement. It is, in a sense, the key to molecular biology because it shows how the great polymer languages, the nucleic acid language and the protein language, are linked together.

The major credit I think Jim and I deserve is for selecting the right problem and sticking to it. It's true that by blundering about we stumbled on gold, but the fact remains that we were looking for gold.

It is not easy to convey, unless one has experienced it, the dramatic feeling of sudden enlightenment that floods the mind when the right idea finally clinches into place.

In my experience most mathematicians are intellectually lazy.

An honest man, armed with all the knowledge available to us now, could only state that in some sense, the origin of life appears at the moment to be almost a miracle, so many are the conditions which would have had to have been satisfied to get it going.

A busy life is a wasted life.

If Watson and I had not discovered the [DNA] structure, instead of being revealed with a flourish it would have trickled out and that its impact would have been far less. For this sort of reason Stent had argued that a scientific discovery is more akin to a work of art than is generally admitted. Style, he argues, is as important as content. I am not completely convinced by this argument, at least in this case.

We have to take away from humans in the long run their reproductive autonomy as the only way to guarantee the advancement of mankind.

God is a hacker, not an engineer

Free will is located in or near the anterior cingulate sulcus.

In the fullness of time, educated people will believe there is no soul independent of the body, and hence no life after death.

Haemoglobin is a very large molecule by ordinary standards, containing about ten thousand atoms, but the chances are that your haemoglobin and mine are identical, and significantly different from that of a pig or horse. You may be impressed by how much human beings differ from one another, but if you were to look into the fine details of the molecules of which they are constructed, you would be astonished by their similarity.

One of the most frightening things in the Western world, and in this country in particular, is the number of people who believe in things that are scientifically false. If someone tells me that the earth is less than 10,000 years old, in my opinion he should see a psychiatrist.

You’re nothing but a pack of neurons.

Since I essentially knew nothing, I had an almost completely free choice.

The ultimate aim of the modern movement in biology is in fact to explain all biology in terms of physics and chemistry.

There is no form of prose more difficult to understand and more tedious to read than the average scientific paper.

If revealed religions have revealed anything it is that they are usually wrong.

A theory should not attempt to explain all the facts, because some of the facts are wrong

The dangerous man is the one who has only one idea, because then he'll fight and die for it.

A good scientist values criticism almost higher than friendship: no, in science criticism is the height and measure of friendship.

Avoid the temptation to work so hard that there is no time left for serious thinking.

It is essential to understand our brains in some detail if we are to assess correctly our place in this vast and complicated universe we see all around us.

There is no scientific study more vital to man than the study of his own brain. Our entire view of the universe depends on it.

The genetic code describes the way in which a sequence of twenty or more things is determined by a sequence of four things of a different type.