BABS1201 Lecture Notes - Lecture 5: Hydrogen Bond, Polymerization, Maurice Wilkins
17 May 2018
School
Department
Course
Professor
BABS1201
16TH MARCH 2018
MACROMOLECULES III
DESCRIBE THE BASIC STRUCTURE OF NUCLEIC ACIDS
× It was initially believed that proteins were the genetic material in cells-
× Proteins vs. DNA
- Proteins have great complexity and 20 monomer building blocks
- DNA has a very regular structure and only 4 building blocks
- Experimental data collected through the 1940’s and early 1950’s, however, began
to suggest that DNA might be the genetic material
× Hershey and Chase experiment of 1953- using bacteriophage T2, a
bacterial virus, Hershey and Chase demonstrated that DNA is the genetic
material
× They took some phage, and labelled the proteins in them with
radioactivity- proteins contain sulfur, unlike DNA- grew it in the presence
of radioactive sulfur, so that the phage’s proteins would become
radioactive
× They took some different phage and grew these in the presence of
phosphorus- DNA contains phosphorus, unlike proteins- DNA thus becomes
labelled with radioactivity
× Incubated bacterium with radioactive phage in two separate flasks
× The phage would dock on the surface of the bacteria, and inject their
genetic material into the bacterium
× Phage needed to be separated from the bacterium- by putting it into a
blender, phage particles are knocked off the surface of the bacterium, but
not sufficient to break open the surface of the bacterium- therefore the
bacteria stay intact
× Then a centrifuge is used- now, the pellet (at the bottom) contains the
bacteria and the liquid part (at the top) contains the phage- inspect to
find where the radioactivity is located
× They discovered that there was no radioactivity associated with the
bacteria when the proteins were labelled with radioactivity, but there was
radioactivity associated with the bacteria when the DNA was labelled with
radioactivity- this showed that it was in fact the DNA that had been
injected into the bacterium, and therefore it is the genetic material
Document Summary
It was initially believed that proteins were the genetic material in cells- Proteins have great complexity and 20 monomer building blocks. Dna has a very regular structure and only 4 building blocks. Experimental data collected through the 1940"s and early 1950"s, however, began to suggest that dna might be the genetic material. Hershey and chase experiment of 1953- using bacteriophage t2, a bacterial virus, hershey and chase demonstrated that dna is the genetic material. They took some phage, and labelled the proteins in them with radioactivity- proteins contain sulfur, unlike dna- grew it in the presence of radioactive sulfur, so that the phage"s proteins would become radioactive. They took some different phage and grew these in the presence of phosphorus- dna contains phosphorus, unlike proteins- dna thus becomes labelled with radioactivity. Incubated bacterium with radioactive phage in two separate flasks. The phage would dock on the surface of the bacteria, and inject their genetic material into the bacterium.
