The chemical structure of DNA III – Genes – the units of inheritance (5/10)
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The chemical structure of DNA III – Genes – the units of inheritance (5/10)


If you’re going to build
anything complicated, you need some sort of plan,
a blueprint, a set of instructions. Now that’s just as true
of living cells as anything else. But they contain the instructions
within themselves. They’re inherited. They’re copied and passed on from generation of cell
to generation of cell. Now what we’re going to do is look
at what the instructions are and how they work. Before we do that,
just stop for a moment and think what
sorts of characteristics any set of inherited instructions
is likely to have. I think they are probably three. First of all, the instructions
have to be stable. They have to last long enough
to be copied and passed on
to the next generation of cells. And there’s the second point. They need to be capable
of being copied and copied accurately. Finally, and most obviously, as instructions
they need to contain information. Well, that’s all very well
but it’s just speculation, theory. What about the reality? The reality is a molecule called DNA. Now you might think
that the structure of a molecule that contains the instructions
for making a complete cell must itself be very complicated. But, in fact,
the basic structure of DNA is remarkably simple. Here’s a model of DNA. Unwind the double helix
and it consists of two long strands that form a ladder-like structure. The strands of DNA are strings
of chemically repeating units, which act as basic building blocks. Each unit contains
a sugar – deoxyribose… …a phosphate group and a base. Together these form a nucleotide. There are actually
four types of base. Adenine. Thymine. Cytosine. And guanine. Within a strand of DNA,
the bases can come in any order. Just how important this sequence is
will become clear later. What’s more, in double-stranded DNA, the bases match up
in a particular fashion. Adenine always pairs up with thymine. And guanine with cytosine. This precise base pairing means
that the base sequence in one strand is complimentary to the sequence
in the other. The base pairs are held together
by relatively weak hydrogen bonds. But when summed up
over the whole DNA double helix, these hydrogen bonds
impart great stability.

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

  1. I don't think you can describe DNA as a blueprint. That seems inaccurate. There is no overall plan in DNA. All living creatures evolved. To say DNA is like a blueprint implies that there was an overall plan to begin with.

  2. @TheWompier, thank you for you're atheistic brainwashed propaganda rhetoric. if you dont see that DNA is a blueprint as to how to build specific protiens then you are out of you're mind. of course it's a blueprint.

  3. @chinamanspeakenlis, well, you must know what you are talking about as you are so fruent in engrish. just say nope to dope kid.

  4. @godrulztheearth it's not cool to bring it up like that… I'm not sided with any religion and consider evolution as an intrinsic aspect of nature, or the creation, whatever you call it. I do agree that there are purposes in life, and i suppose one can consider that a "plan" since it describe how one will try to achieve survival, pleasure or awareness…whatever drives it; Sorry Wimpier!

  5. DNA is complicated, a hydrogen atom is complicated. it's just that when you compare DNA to proteins, then the proteins may be more complex. But lifes design is pretty complex whether you look at DNA or proteins

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