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Post by Pem on Jul 10, 2008 19:00:22 GMT -7
Lecture 1: Chemical Nature of DNA
DNA is an acronym for Deoxyribonucleic Acid. It is present in the majority of all cells on earth and controls the very nature of life. It is a simple molecule consisting of only Carbon, Oxygen, Hydrogen and Nitrogen. The Elements form together to form units known as nitrogenous bases, the forms that are found in DNA are adenine (A), guanine (G), cytosine (C), and tyrosine (T). Adenine and guanine are purine compounds while cytosine and tyrosine are pyrimidines.
Due to their shape and nature they are able to bind with each other specifically, a purine with a pyrimidine. Now with this in mind Adenine binds with Tyrosine and Guanine binds with Cytosine, exclusively. Knowing that type of binding occurs and is favoured we are able to predict a method of self replication. This is the most important characteristic of DNA, although, as we shall see, it is not 100% fool proof.
These nitrogenous bases are bound to a sugar forming a nucleoside and this is further bound to a phosphate backbone forming nucleotides. Long chains of phosphate groups bound to sugars form to create the double helixed molecule described as DNA.
In the next lecture I shall discuss how this simple molecule is able to replicate itself, try to find out on your own.
(Pictures to be added later)
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Post by Pem on Jul 24, 2008 6:36:27 GMT -7
Lecture 2: Replication of DNA (I apologize this is largely unedited I just wanted to post it before I left for my trip)
Alright, now that we have established what DNA is and what it is made of, perhaps you’d have noticed that the two strands fit nicely together in sort of a puzzle piece arrangement.
Have you managed to come up with a way in which they can duplicate themselves? If you imagined them separating in some way then you are correct.
Image DNA as a great big puzzle surrounded by pieces that could fit into it. When you pull the puzzle apart (DNA) the pieces that can fit (nucleotides)are now able to be placed into position by a sort of piece placer. This placer of nucleotides into DNA is an enzyme called DNA polymerase; this enzyme allows DNA to replicate as well as having a multitude of other functions which we can discuss later.
Now then, we had previously a double strand of DNA pulled apart to form two single stands of DNA, and then had nucleotides added to them to create two separate double strands. These two double strands are identical in the order, amounts and placement of nucleotides.
For example
Strand 1 AGTCGTGCATG Duplicate TCAGCACATAC
Strand 2 TCAGCACATAC Duplicate AGTCGTGCATG
You might have noticed that the duplicate of each strand is identical to the opposite strand. The actual mechanism for DNA replication is much more complicated than then but for that topic at hand this is all you need to know. What is important is that DNA is able to create copies of itself and in the next two lectures the significance of this will become much clearer.
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