RedOne77
Active Member
Interesting, but I'm still not inclined to give astro-projection any more weight, sorry. There just isn't enough hard evidence to convince me, but remember I'm skeptical of near death experiences too.
Think of it more as a sound bite that you would hear on the media. Rarely are sound bites all there is too it, but for getting an idea across quickly and easy to remember, they are good at doing that.
And usually people add in words like "like" or "as" to tell the audience that it is a simile/metaphor.
It is a shape characterized by smooth curves, the two rails of the DNA ladder are twisted into this shape.
The backbone of DNA is the "rail" part if you think of DNA as a ladder. It is composed of an alternating sugar and a phosphate group, called the sugar-phosphate backbone of DNA.
That would be the "A, C, T, G" part that most people refer to when they talk about DNA. It is the sequence of these bases that is important when talking about heredity, mutations, and what determines which proteins get produced in an organism.
When it comes to the structure of DNA, the most famous part about it is the famous Watson and Crick paper of 1953 where Rosalind Franklin used X-Ray Crystallography on DNA and found that it was an alpha helix. Based on the data they were able to deduce the basic structure; a sugar-phosphate backbone with the bases in the middle. As far as I know they basically used different models and saw which one fitted the data the best. One of the harder parts was determining the rules of how the bases fit together (they are not the same size). Eventually they were able to determine that each rung of the DNA ladder had to consist of one purine (A or G) and one pyrimidine (C or T).
As far as the experiments showing that DNA is the molecule of inheritance, the big experiments were done by Griffith, Avery and Hershey-Chase.
Just a quick summery, Griffith used bacteria, "S" and "R" strains, and injected it with mice. If the mouse was injected with the pathogenic "S" strain it died, however it lived if it was injected with the benign "R" strain. When he killed the S strain through heat, and injected it into the mouse with a living R strain, the R strain changed into the S strain and killed the mouse.
Avery took this experiment one step further by tracing which molecule was inherited by the R strain to turn it into the S strain. He looked at lipids, proteins, carbohydrates and DNA. And it turned out that the molecule inherited was the DNA.
Hershey-Chase did a similar experiment to Avery only with T2 phages and E. coli. Basically the T2 phages are made up of only protein and DNA, they inject something (DNA) into the E. coli to reproduce. You tag the DNA with radioactive phosphorus and proteins with radioactive sulfur, see which one was injected and that is the molecule of inheritance. The data showed that it was indeed DNA that is the molecule of inheritance.
You can probably google any of these things and come up with a lot more info.
You're reading too much into the purpose idea. Science is riddled with analogies, and sometimes it is hard to separate them. Technically, DNA doesn't have a "purpose", we just assign a 'purpose' to it for our convenience. DNA does have function, and through its functionality it can do certain things.
DNA is what is called an 'informational molecule'. It has information in it, but the information is not a laymens term. And DNA isn't the only factor in a persons structure or chemistry - there are other factors that don't rely on the sequence of the DNA.
An enzyme is a biological catalyst. Every single chemical reaction that goes on inside an organism is carried out by an enzyme. Enzymes either break down, or build up molecules by lowering the amount of energy needed to start the reaction. Enzymes have something called an "active site" where the molecules (reactants) bind to the enzyme. These reactants are called the substrate. However, the enzyme is substrate-specific, meaning that only the substrate with the right shape (and right chemical properties) will bind to the active site. That is what is meant by the enzyme being a lock and the substrate being a key.
The enzyme is not a static structure, and the binding site (active site) is continually being re-shaped. What happens when the substrate starts to bind, is that the active site structurally changes and can wrap around the substrate.
You can read about enzymes on the wiki page too: http://en.wikipedia.org/wiki/Enzyme
