Question

Describe Avery, McLeod, and McCarty's experiment. State its significance.

Answer 1

Hint: Previously it was thought that proteins transfer the genetic information, but later, experiments conducted by the Griffith reveals the DNA is responsible for genetic material transfer, whereas Avery, McLeod, and McCarty's done experiments to know the biochemical nature of this material

Complete answer:
Avery, McLeod, and McCarty's experiment determines the nature of genetic material in in-vitro condition.
- Previously Mendel discovered the inheritance, experiments on the law of inheritance was discovered by Mendel
- But there is no evidence that the material actually responsible for the transmission
- Based on previous Mendel experiments, Griffith conducted the experiments on streptococcus pneumonia.
- Where they collect the streptococcus pneumonia and cultured the bacteria on cultured plates.
- While culturing they identified two strains, one is smooth shiny bacteria said to be S strain, and rough bacteria said to be R strain.
- The difference between the S and R is the presence of a mucous coat on S strain, which is absent in R strain.
- They injected into Mice and observed, Mice injected with S strain develops pneumonia, while Mice injected with R strain was alive.
- Later they heated the strains and injected and concluded that transferring things is the genetic material.
- Whereas Avery, McLeod, McCarty continued the Griffith experiment and come to know the biochemical nature of the genetic material
- Avery and his co-extracted proteins killed S strain and collected some proteins such as DNA, RNA, and some other molecules.
- So finally they discovered that DNA is the genetic material and it is responsible for transformation into R strain in bacteria.

Note: Avery and his team also observed that some of the enzymes such as protease ( responsible for protein digestion), and RNase ( responsible for RNA digestion) did not inhibit the transformation during the experiment, while DNase did.