How did Hershey and Chase differentiate between DNA and protein in their experiment while proving that DNA is the genetic material?
Solution and Explanation
Hershey and Chase worked with bacteriophage and E. coli to prove that DNA is the genetic material. They used different radioactive isotopes to label DNA and protein
coat of the bacteriophage.
They grew some bacteriophages on a medium containing radioactive phosphorus (32P) to identify DNA and some on a medium containing radioactive sulphur (35S) to identify protein. Then these radioactive labelled phages were allowed to infect E. coli bacteria. After infecting the protein coat of the bacteriophage was seperated from the bacterial cell by blending and then subjected to the process of centrifugation. Since the protein coat was lighter it was found in the supernatant while the infected bacteria got settled at the bottom of the centrifuge tube. Hence it was proved that DNA is the genetic material as it was transferred from virus to bacteria.
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Concepts Used:
Non-Mendelian Genetics
The term - non-mendelian inheritance refers to any pattern of heredity in which features do not separate according to Mendel's laws. These principles describe how features linked with single genes on chromosomes in the nucleus are passed down through generations.
Types of Non-Mendelian Inheritance
Codominance Inheritance
It is a form of incomplete dominance in which both alleles for the same feature are expressed in the heterozygote at the same time. For example, the MN blood types of humans.
Incomplete Dominance
In a heterozygote, the dominant allele does not always completely cover the phenotypic expression of the recessive gene, resulting in an intermediate phenotype which is referred to as "incomplete dominance”.