Question

DNA experiment

1. Why was it thought that DNA and not protein would turn out to be the genetic material?

2. What evidence was there for DNA?

Answer 1

Ans 1. According to the experiment performed by Hershey and chase it was concluded that DNA was the genetic material and not the protein. The protein was found to be the protective coat of the bacteriophase but the internal DNA is what conferred its ability to produce progeny inside a bacterium.

Ans 2. The evidance that the DNA was the genetic material was give by the Hershey and chase experiment where they infected a bacteria by T2 bacteriophage, attaching to it and they labeled the phage DNA with radioactive Phosphorus-32.They found that the radioactive element left on the phage's DNA was only in the bacterium, and not in the phage. They perform the same experiment with labels on the phage protein with radioactive Sulfur-35, after the attachment of phage to bacterium the radioactive element was found in the phage, but not in the bacterium. As this shows the protein coat remained outside of the bacteria whereas the DNA was incorporated inside the bacteria. Thus it was concluded that the DNA is only the genetic material which is tranferred from parents to the offspring.