The chemical structure of DNA II – Genes – the units of inheritance (4/10)
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The chemical structure of DNA II – Genes – the units of inheritance (4/10)

The breakthrough was in 1953, thanks to Cambridge scientists,
Francis Crick and James Watson, in the most celebrated research
of the 20th century. Using the x-ray pictures of DNA, taken by Rosalind Franklin
and Maurice Wilkins, they struggled to make the data
about the spaces between the atoms fit into a structure that made sense. When they had finished,
it did make sense but in a more profound way than a structure
of any molecule before or since. The most important thing
about that structure was not that it was a double helix, which is the icon of the 20th century
we all are aware of, but the fact that it was
a very long linear molecule and that these bases,
the A, G, C, T symbols, were distributed linearly along it. They spotted
and confirmed the notion, that people have been fighting
against that it was digital because it seemed unreasonable that something sort of soft
and squidgy and lifelike like us would be coded for
in this hard, digital fashion. But it is so
and that’s the breakthrough, which now we’re exploiting today
to actually read out that code. Although the double helix
looks complicated, what it does is very simple. Crick and Watson
had opened up a world not of chemistry but of information. Each strand of DNA
carries a set of four bases abbreviated to A, C, T and G. The bases can occur in any order
along the length of the molecule and this is how the information
is carried, just as the letters
of the alphabet make words. But the crucial thing is the way the bases on the opposite strand
are joined. Chemistry allows A only with T,
C only with G. And they saw, also,
and this is the famous sentence, “it has not escaped our attention that this provides a mechanism
for replication” because they saw that if you pulled the two halves
of the double helix apart, then used those same rules
to reconstruct new strands, you’d have two new double helices
looking just like the old one. You had replicated DNA
and as Francis Crick said, “That’s the secret of life.” Crick and Watson realised that each strand could act
as a template for the other. If you split them apart
into two single strands and then throw in a mixture
of A, C, T and G, the bases can only join up
in the right places. A T opposite every A,
an A opposite every T, a C opposite every G,
a G opposite every C and you have accomplished
one of the great tricks of nature. You’ve taken one copy of the code
and made two identical perfect copies that can pass on
to the next generation. Through chemistry and physics,
Crick and Watson have discovered how the instruction for life
are passed on.

5 thoughts on “The chemical structure of DNA II – Genes – the units of inheritance (4/10)

  1. it's a shame that Rosalind Franklin's name is not usually mentioned as significantly as she deserves. she gave her life to this.

  2. Any video that misses mentioning the fact that Watson and Crick defrauded Rosalind Franks is summarily deficient to say the least! 

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