1.23.07 - 1.23.07 DNA is a polymer, a chain of smaller...

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1.23.07 DNA is a polymer, a chain of smaller units, the units are called nucleotides, which have three components Nucleotides: contain a sugar (either deoxyribose or ribose) – the defining difference between DNA and RNA (other differences are observed but this is the defining difference o DNA is deoxyribose o RNA is ribose o Only difference is deoxyribose has a hydrogen where a ribose has an OH o The carbons on deoxyribose and ribose are numbered, there are 5 carbons on the sugar and there are five points in the ring, but one of the carbons is outside of the ring and one of the points of the ring is actually an oxygen, the other points are carbons o The way to number it is to start with the exocyclic carbon, this is the 5’ carbon, then take the other carbons in order. The 5’ carbon is attached to the 4’ carbon, then the 3’ which is attached to the 2’, until the 1’ which is attached to the oxygen o 2’ carbon is a hydroxyl in a ribose o 2’ carbon has a Hydrogen and is deoxygenated when compared to ribose o Also contains a nitrogen containing base, there are four possible bases in DNA, the nucleotide contains Adenine, thymine, cytosine and guanine o Four possible bases in RNA with the substitution of uracil for the thymine in RNA, there is very little chemical difference between T and U, a methyl group in thymine is a H in Uracil o Need to know general shapes of the bases Adenine and guanine are both purines, two rings fused together Others are pyrimidines made of a single ring (TCU) AGs are pure – purines or aggies eat PURINa o The base is attached to the 1’ carbon of the sugar which is actually another way that you could remember the order of the carbons, bases attach to the 1’ and then count your way around up to 5’ o Nucleotide will have 1, 2, or three phosphates Phosphates attach to the 5’ carbon, in series if there are multiple phosphates (connected one phosphate to the next) o Nucleotides are named to designate what those components are Which sugar is it? Look at 2’ carbon and see if it is OH (ribose) or H (deoxyribose) Hydrogen can be omitted and assumed to be there, Oxygen cannot Use a lowercase d for deoxy Which base is it? See if purine or pyrimidines by number of rings Adenine- use adenosine so now we have…dA (deoxyadenosine) How many phosphates are there? If there are 2 – diphosphate Now we have dADP (deoxyadenosinediphosphate) Which does ATP have? If you don’t say dATP, then it is ribose, so the ribose does not get designated, therefore there is a ribose sugar The base is adenine There are three phosphate groups One more example dGP deoxyguanosinemonophosphate What about putting nucleotides together? o
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This note was uploaded on 04/07/2008 for the course BIO 325 taught by Professor Saxena during the Spring '08 term at University of Texas.

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1.23.07 - 1.23.07 DNA is a polymer, a chain of smaller...

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