{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Chapter 16 - Chapter 16 Double helical model o DNA...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 16 - Double helical model o DNA substance of inheritance o Nucleic acids direct own replication from monomers o T.H. Morgan genes located along chromosomes - Griffith’s Experiment (1928) o Trying to find vaccine form pneumonia o Fredrick Griffith studied streptococcus pneumonia bacteria that caused pneumonia in mammals had 2 strains 1 pathogenic (disease causing) and 1 nonpathogenic (harmless) o when he killed the pathogenic bacteria with heat then mixed the cell remains with living bacteria of nonpathogenic strain, some of the living cells became pathogenic newly acquired trait of pathogenicity was inherited by ALL the descendants of the transformed bacteria o Griffith defined as – TRANSFORMATION- change in genotype and phenotype due to assimilation of external DNA by a cell. o **figure 16.2, pg 306 Griffith’s Exp. On Rats - Oswald Avery o Focused on 3 main candidates: DNA, RNA (the other nucleic acid), and protein. o In separate samples, he used specific treatments that inactivated each of the 3 types of molecules. tested each for its ability to transform love nonpathogenic bacteria. o Only when DNA was allowed to remain active did transformation occur. DNA = transforming agent - (1944) Avery, McCarty and MacLeod announced transforming agent was DNA o Represent Griffith? (+) enzymes to dest. Lip. 1. Lipids 2. Carbs 3. Protein 4. RNA o Transformation still occurred only DNA was left. - Hershey and Chase Exp. (1952) o Performed exp. Showing that DNA is the genetic material of a phage known as T2. o Bacteriophage- “bacteria- eaters”- viruses that infect bacteria. Can also just be called “phages”. A virus = little more than DNA enclosed by protective coat, often is a simple protein. To reproduce, a virus must infect a cell and take over the cell’s metabolic machinery.
Image of page 1

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

View Full Document Right Arrow Icon
o T2 composed almost entirely of DNA and protein T2 phage could quickly turn E. coli cell into a T2 producing factory. T2 could reprogram host cell to produce viruses. o Hershey and Chase exp. fig. 16.4, p. 307 Which was the viral component- DNA or protein- responsible? Their exp. Showed that only 1 of 2 components of T2 enters the E. coli cell during infection To find out, they added sulfur to tag the protein since protein contains sulfur and they added phosphorus to the DNA to tag it. They tested 2 samples shortly after the onset of infection to see which type of molecule (protein or DNA) had entered the bacterial cells and therefore would be able to reprogram it. They found that the phage DNA entered the host cells but the phage protein did not. when these bacteria were returned to a culture medium, the infection ran its course, and the e. coli released phages that contained some of the radioactive phosphorus, showing that the DNA inside the cell played an ongoing role during the infection process.
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern