Experiment3-DNA

Experiment3-DNA - Experiment 3(Lab Periods 3 and 4 Extraction of DNA from Bacteria The first demonstration that pure DNA could transmit genetic

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Experiment 3 (Lab Periods 3 and 4) Extraction of DNA from Bacteria The first demonstration that pure DNA could transmit genetic information from one kind of cell to another was reported in l944 by Avery, McCarty and MacLeod, who investigated the chemical identity of the "transforming principle". Although their proof was biologically and chemically rigorous, it was not immediately accepted by biologists, biochemists and geneticists because nucleic acids were regarded as too simple to carry information. Gradually, other kinds of investigations provided reasons to believe that genes were, indeed, composed of DNA, and when the double-helical structure of DNA and the triplet nature of its information content were elucidated, it became clear how DNA molecules could serve as genes. In this experiment, you will attempt to extract DNA from a species of bacteria ( Bacillus subtilis ) and observe the stringy nature of DNA molecules. The DNA you lift out of the tube at the end would be suitable for introducing heritable information into another kind of bacterium. You will then use spectrophotometry to calculate the amount of DNA that you have extracted from the cell by resuspending the DNA in solution and measuring A 260 . Finally, this will allow you to calculate your yield of DNA per bacterium. You will be provided with l0 ml of a culture of Bacillus subtilis from which you will plate a sample in order to calculate the concentration of cells. You will collect the rest of the cells by centrifugation and wash the cells in Lysis Medium. The washed cells will then be treated with an enzyme (lysozyme) that dissolves their cell walls, a detergent (SDS) that dissolves their cell membranes, and a second enzyme (pronase) that dissolves their proteins. The only large molecules left intact will be nucleic acids. These will be "salted out" and mildly dehydrated with ethanol so that the long DNA molecules will become entangled with each other and will stick to a glass rod. Once you have isolated the DNA you will measure the amount you have isolated by using spectrophotometry.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/30/2012 for the course BIO 2004 taught by Professor Morton during the Spring '11 term at Columbia.

Page1 / 4

Experiment3-DNA - Experiment 3(Lab Periods 3 and 4 Extraction of DNA from Bacteria The first demonstration that pure DNA could transmit genetic

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online