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    Keep seeing this as an essay title and in questions with quite a few marks. Talking about DNA is easy, but relating it to the structure is hard aside from obvious things like the double helix and compact shape. Any ideas?
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    -talk about anitcodons
    -how the "sense" strand helps with transcription
    - maybe go in some deatil about how transcription and translation occur.

    The following is a question and the answer. it talks about the DNA structure in depth.
    Question

    Give an account of the structure and replication of deoxyribonucleic acid (DNA)

    Answers
    DNA is a macromolecule polymer made of subunits called nucleotides. The nucleotides are arranged in two chains, which are coiled into a spiral shape called a double helix; DNA is the molecule from which the gene alleles on the chromosomes are made;As with all nucleotides, those in DNA have three parts. These are a pentose sugar called deoxyribose, a phosphate group and a nitrogenous base;The sugar and the phosphate are exactly the same in every nucleotide, but the base varies. There are four bases in DNA and each nucleotide contains one of them. The bases are called Adenine, Guanine, Thymine and Cytosine. (A,G,T and C for short);The nucleotides are joined in a specific order. The order of the nucleotides means that the bases they contain are in a certain order, it is this order which forms the genetic code;The sugar and phosphate join together to make the backbone of the DNA molecule. The 3’ carbon on one sugar is joined to the 5’ carbon on the next by means of a phosphate bridge, like this;Each time the sugar joins to a phosphate, a molecule of water is eliminated in a condensation reaction;This sugar-phosphate-sugar bond is called a phosphodiester bond;The process repeats so that a very long chain of nucleotides is made, a polynucleotide. Note that the bases protrude from the side of the chain;There will be a spare 5’ sugar atom at one end of the chain and a spare 3’ atom at the other. The chain thus has a 3’ to 5’ direction reading up the page;In DNA a second polynucleotide chain forms next to the first, but this runs in the opposite direction. The chains are therefore described as antiparallel; The bases now find themselves opposite one another and bond with weak hydrogen bonds. When this occurs Adenine always pairs with Thymine (A-T) and Guanine with Cytosine (G-C). There is a good reason for this complementary pairing;Adenine and Guanine both have a double ring structure and are classified chemically as Purine bases;Thymine, uracil and Cytosine all have a single ring structure and are classified as Pyrimidines;The actual process of DNA replication is simple. To begin with one strand in the DNA duplex is nicked by the enzyme DNA topoisomerase, allowing part of the molecule to unravel to form a replication fork (the DNA is replicated a bit at a time and the whole molecule is never completely uncoiled);Next, the enzyme DNA helicase splits the two strands by breaking the hydrogen bonds. This exposes the bases;DNA polymerase enzyme then moves along the exposed bases sequences, creating a new complementary strand as it goes. DNA polymerase reads the exposed code from the 3’ to the 5’ end and therefore assembles the new strand from the 5’ to the 3’; Several molecules of DNA polymerase act simultaneously, each assembling a separate section of the new strand of DNA. Each DNA polymerase is preceded by an RNA polymerase enzyme, which constructs an RNA primer to guide the action of the DNA polymerase;These new DNA segments are then joined together by the enzyme DNA ligase. The two new daughter molecules then coil up again to reform the double helix structure. This process occurs during the S-phase of the cell cycle;

    OR YOU COULD SAY THIS.

    1) DNA is a polypeptide/polymer-monomers called nucleotides/ any ref to DNA made of nucleotides; 2) nucleotides consists of deoxyribose, phosphate and a base; 3) bases are adenine, guanine, cytosine and thymine, 4) A and G are purines 5) C and T are pyrimidines 6) DNA is a double helix; 7) phosphate-sugar linked to form strands/ sugar-phosphate backbone/ ref. to phospho-diester bonds; 8) Strands are antiparallel/run in opposite directions; 9) pairing of A and T, C with G; 10) hydrogen bonding between base pairs; 11) replication semi-conservatrive/ 1 old and 1 new strand in each daughter molecule; 12) replication occurs during interphase/s phase; 13) strands separate by breaking H bonds; 14) new strand synthesised by DNA polymerase; 15) complementary base-pairing in daughter strands/ use of correct base-pairing to give accurate copy; 16) ref. to unwinding/separation of strands by helicase; 17) 5' to 3' direction of synthesis by DNA polymerase; 18) lagging/ strand sections joined by ligase;
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    Thanks a lot, you obvioulsy know your stuff very well.
    When replicating the 3' to 5' strand, is DNA ligase used, and its replicated in shorter sections, or is my memory misinforming me?
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    Im not really sure, but if you replicate the the 5’ to 3’ strand by joing nuleiotides and using dna polymerase it will produce a 3' to 5' strand.

    But if you replicate the stand into smaller sections, would it not break the bond formed by the condensation reaction thats hold the 3 and 5 togther, im not sure :confused:
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    Ok, I looked it up.
    Polymerase only works in the 5' --> 3' direction, and ligase in the 3' --> 5' direction (if you're interested)
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    Thanx alot for finding out
 
 
 
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