Isolation of genomic DNA fall 2011

Isolation of genomic DNA fall 2011 - Lab topic:...

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Lab topic: Macromolecules 2: Polysaccharides, nucleic acids Isolation of genomic DNA Introduction DNA molecule is a long polymer built of four different nucleotide monomers. The nucleotides are composed of three different components: nitrogen base, deoxyribose sugar and phosphate group. What makes nucleotides different is the nitrogen base. There are four of them: adenine (A), thymine (T), guanine (G) and cytosine (C). The polynucleotide chain, of DNA is made by the connection of the phosphate group to the deoxyribose of the next nucleotide. Various combinations of these nucleotides create unique DNA sequence or genotype, which carries the genetic information in the cell. However, DNA molecules that comprise the chromosomes are not single stranded. Chromosomal DNA is double-stranded molecule with two single strands of DNA (polynucleotide chains) twisted around each other in a helical structure and held together by hydrogen bonds between nitrogen bases. Chromosomal or genomic DNA of all cellular organisms is double-stranded. The structure can be viewed as a twisted ladder in which the hydrogen bonded nitrogen bases are the rungs and the phosphate-deoxyribose backbones the sides. The nitrogen base A can pair by hydrogen bonds only with T and G only with C. We say that the two strands are complementary. The length of any double- stranded DNA molecule is given in terms of base pairs (bp). If a DNA strand contains over a thousand base pairs it is measured in kilobases (1kb = 1000bp). If there are over a million base pairs in a strand the unit of measure is megabases (1Mb = 1000 kb). If over a billion base pairs then the unit of measure is gigabase (1Gb = 1000Mb). A human cell contains 23 pairs of chromosomes with total length of 3 Gb. The bacterium E. coli has one circular chromosome with total length of 4 Mb, while the bacteriophage lambda has a linear chromosome which is 50 kb long. A lot of important work has been done with DNA. For many of these studies the first step is the isolation and purification of DNA. In eukaryotic cells (but not prokaryotic) DNA is associated with basic proteins called histones. Histones are strongly positively
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This note was uploaded on 09/26/2011 for the course MATH 120508 taught by Professor Jdoug during the Fall '08 term at Drexel.

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Isolation of genomic DNA fall 2011 - Lab topic:...

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