Molecular Basis of Inheritance

Five. Molecular Basis of Inheritance

DNA is the genetic material in most of the organisms i. Prepared two cultures of bacteriophage- In one, protein coat were radioactively labelled with thirty-five S In second, DNA is radioactively labelled with thirty-two P.

ii. Radioactive phages were used separately to infect E. coli. iii. After infection, the E. coli was blended and centrifuged. Inference:-

Viral DNA gets into bacterium and the protein remains outside.

The DNA

DNA versus RNA

DNA

RNA

- Acts as the genetic material in some viruses (e.g.: TMV, QB bacteriophage)

Acts as the genetic material in most of the organisms

- functions as messenger (mRNA).

- Act as enzyme (ribozyme).

DNA was derived from RNA

RNA is the first to evolve

RNA is better for the transmission of genetic information

DNA is a better genetic material

: Chemically less reactive and structurally more stable due to

: easily degradable due to

· Being single stranded

· Being double stranded

· Presence of thymine (five-methyl uracil).

· Presence of uracil (less stable compared to thymine).

· Absence of two-prime hydroxyl in deoxyribose sugar

· Presence of two-prime hydroxyl in ribose sugar (a reactive group)

Resist mutation by repair mechanism

Mutate at a faster rate

DNA is dependent on RNA for synthesis of proteins DNA to RNA to Protein

Can directly code for the synthesis of proteins

Central Dogma of Molecular Biology

Proposed by Francis Crick