Problem 1. In the 1940s, a pressing question in biology was whether DNA or prote
ID: 215222 • Letter: P
Question
Problem 1. In the 1940s, a pressing question in biology was whether DNA or protein was responsible for the transmis- sion of genetic information. A simple system to study this is a bacteriophage, a virus that injects a substance into Es- cherichia coli, thereby transforming the bacteria's genetic material. Design an experiment using radioactive tracers that could determine whether DNA or protein was the injected substance. Hint: DNA contains many phosphorus atoms but no sulfur, whereas protein has many sulfur atoms but no phosphorus. Alfred Hershey and Martha Chase performed such an experiment in 1952. n uinoinho narticle is fired directly at a stationaryExplanation / Answer
By performing the Hershey-Chase series of experiments we can prove that the DNA (deoxyribonucleic acid) is responsible for bacterial transformation, but not the proteins. In this, the first step of experiments is the preparation of bacteriophage labeled with radioactive isotopes. They are then inserted into the bacteria, followed by bacterial incubation.
The incubated bacteria release number of bacteriophages now and these progeny should be examined for the presence or absence of radioactive isotopes.
The bacteriophage is a viral vector that can infect bacteria; the virus contains DNA packed with protein core. If bacteria are infected with a viral vector, part of the virus enters the bacterium, and after approximately 4hrs of incubation, the bacteria release viruses in dozens.
In the parent bacteriophages, the phosphorus present on deoxyribose-phosphate (of DNA backbone) is labeled with phosphorous radio-isotope (32P), followed by their insertion into the bacteria and incubation. The same is repeated using sulfur isotope (35S), because only amino acids of proteins contain sulfur.
The resultant progeny shows 1/3rd of the original phosphorus isotope and lack sulfur isotope, which indicates the DNA, is responsible for the bacterial transformation.
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.