Questions on DNA Synthesis and Gels 1. Name three pyrimidine bases, and what pur
ID: 280011 • Letter: Q
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Questions on DNA Synthesis and Gels 1. Name three pyrimidine bases, and what purine bases do they base pair with? 2. When a DNA chromosome has been replicated, there are now two DNA molecules and they are both double stranded. Where are the two old strands of DNA? 3. During DNA replication, a deoxy-nucleotide is added to the growing strand of DNA. To which carbon atom on the deoxyribose is the new nucleotide added? 4. If you loaded your DNA sample to a gel and the well was at the top of the gel, at which end of the gel should the negative electrode be connected? 5. Why do large fragments of DNA run slower through a gel?Explanation / Answer
1. There are two kinds of nitrogen contain bases - Pyramidines nad purines.purines consist of a six membered and five membered nitrogen chain fused together.Pyrimidines have only a six membered nitrogen containing ring.
There are 4 purines nad 4 pyrimidines.
Pyrimidines
Uracil - 2,4 dioxypyrimidine
thymine - 2,4 dioxy 5 methyl pyrimidine
cytosine - 2 oxy 4 amino pyrimidine
orotic acid - 2, 4 dioxy 6 carboxy pyrimidine
purines
adenine - 6 amino purine
guanine - 2 amino 6 oxy purine
hypoxanthine - 6 oxy purine
xanthine - 2,6 dioxy purine
Base pairing : Adenine always pairs with Thymine, guanine always pairs with cytosine,
2. DNA is unwound and its a nucleotide that match to make two new strands.The base on the old strand dictates the base appears on the new strand.it is semiconservative replication, each strand in the double helix acts as a template for the synthesis of new , complementary strand. During DNA replication ,one new strand ,the leading strand is made as a continous peice ,the other old lagging strand is made into small pieces.
3.In the DNA, the new nucleotide is added to the 3rd carbon atom and phosphate groups are added to 5th cardbon atom.
4.DNA ia negatievly charged , therfore when an electric current is applied to the gel,Dna will migrate towards the postive charge of the electrode.
5. Gel electrophoresis is a commom method that used for the seperation of DNA, smaller molecules migrate through the gel more quickly therefore the larger strands migrate more slowly, therefore they will travel a shorter distance.as a result, the molecules are seperated by size.
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