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Lab 6: Molecular Biology The Effect Of Different Restriction Enzymes on the Distance the DNA Strands Migrated Through the Gel Electrophoresis/Agarose Gel By: Emily Zheng AP Biology Pd 7&8 Mr. Smith 13 April 2018 Lab 6: Molecular Biology
Zheng 1 Introduction: Bacteria Escherichia coli short for E. coli are one of the most ideal organism that are commonly used by molecular geneticist for recombinant DNA researches. These bacteria Plasmids are small circular DNA molecules that carries genetic information, and are usually extra chromosomal; which means that they exist apart from the chromosomes in most bacterial species. Some plasmid replicate only when the chromosome replicates and only exist in single copies, but others can replicate rapidly and could have about 10-200 copies in a cell. Some bacteria known as the R plasmid contain genes that resistant to certain anitibiotics like ampicillin, kanamycin, and tetracycline.. Restriction endonucleases or commonly known as the restriction enzymes, are enzymes that actually cut the phosphate backbones of a DNA. These enzyems recognize specific DNA sequences in double-stranded DNA(based on the type of enzymes they are), which is usually about four to six base pair sequence of nucleotides, and then digest the DNA at these sites. The resulting fragments of DNA of varies in different lengths and sizes. Some restriction enzymes cut cleanly right through the DNA double helix at the same position on both strands, creating a blunt end, while some endonuclease cut DNA at specific sites, producing “overhang” or sticky ends. By using the same restriction enzyme to cut DNA from different organisms, the sticky ends produced will be complementary to each other and the DNA from the two different animal can be recombined.The restriction enzymes are named according to a system of nomenclature. The first letter represents the genus name of the organism. The next two letters come from the species name. If there is a fourth letter, it stands for the strain of the organism. Finally, if there are Roman numerals, it represents whether that particular enzyme was the first or second etc. isolated in that category. In this lab electrophoresis chamber, there is placed an agar gel. This gel has wells in it for the samples of DNA to go into. The agarose gel is covered in a
Zheng 2 buffer so that the DNA is in a neutral pH solution. When DNA enters a electric field, the speed or mobility in which it moves are greatly influence on the charge of the molecule, strength of electric field,size and shape of molecule and the density of the gel. Since the phosphate groups backbone of the DNA are negatively charged, the whole molecule takes on the negative charge.

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