Course Hero Logo

Fact that it also finally laid to rest the question

Course Hero uses AI to attempt to automatically extract content from documents to surface to you and others so you can study better, e.g., in search results, to enrich docs, and more. This preview shows page 15 - 17 out of 19 pages.

fact that it also finally laid to rest the question aboutthe chemical nature of the genetic material, first askedsome 75 years earlier, went unnoticed.FIGURE 2The Hershey–Chase experiment showed that the genes ofT2 bacteriophage, a type of virus that infectsE. coli, are made of DNA.Hershey and Chase knew that T2 bacteriophage was made of DNA andprotein. We now know that the DNA contained a protein “head,” whichis attached to a “body” and “legs,” also made of protein. Hershey andChase added some T2 bacteriophages to a culture ofE. colibacteria, andthen waited a few minutes to allow the viruses to inject their genes intothe cells. They then agitated the culture in a blender in order to detachthe empty virus particles from the surfaces of the bacteria. The culturewas then centrifuged, which collects the bacteria plus virus genes as apellet at the bottom of the tube, but leaves the empty virus particles insuspension. Hershey and Chase found that the bacterial pellet containedmost of the viral DNA, but only 20% of the viral protein. Hershey andChase also allowed some of the bacteria to complete their infectioncycles. The new viruses that were produced inherited 50% of the DNAfrom the original T2 bacteriophages, but only 1% of the protein.centrifugecontinueinfectioncyclevirus attachedto bacteriapelletof bacteriavirus nowdetachednew viruses contain 50%of the original virus DNAbut only 1% of the proteinwait a few minutesfor infection tooccur, then agitatepellet contains 70% ofthe virus DNA, but only20% of the virus proteinproteinDNARESEARCH BRIEFING 2.2
26CHAPTER 2:DNAmost quickly and the longer ones the slowest. By the time they get to theend of the capillary they have formed bands, each band containing themolecules that are one nucleotide longer than those in the preceding band(Figure 2.20B).Each of the four dideoxynucleotides emits a fluorescent signal of a differentwavelength. A fluorescence detector is therefore used to identify which ofthe four dideoxynucleotides is present in each band. By identifying whetherthe dideoxynucleotide is an A, a C, a G, or a T, the detector is able to build upthe DNA sequence of the cloned fragment nucleotide by nucleotide (Figure2.21). The sequence can be printed out for examination by the operator, orentered directly into a storage device for future analysis.CACCGCATCGA AATTAACTTC CAAAGTTAAGCTTGGddAddTddTddCddGddNTPs – each emits adifferent fluorescent signalsequencing reactions,fractionation of productsfluorescent bandsmove past the detectorddAddAddGddCddCddGimaging systemdetector(A)102030(B)FIGURE 2.20Capillary gel electrophoresis.(A) A capillary gel. (B) The principle behindseparation of DNA molecules by capillarygel electrophoresis. During electrophoresis,the DNA molecules become separatedaccording to their lengths, the shortest onesmoving most quickly through the gel. Themolecules therefore form a series of bandsin the capillary tube.

Upload your study docs or become a

Course Hero member to access this document

Upload your study docs or become a

Course Hero member to access this document

End of preview. Want to read all 19 pages?

Upload your study docs or become a

Course Hero member to access this document

Term
Fall
Professor
staff
Tags
DNA, www garlandscience com design, Genetics Brown

Newly uploaded documents

Show More

Newly uploaded documents

Show More

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture