Biologist Prof. Obaid Siddiqi who revealed "Stop Codons" passed away

The renowned biologist, Prof. Obaid Siddiqi (81) died due to injuries after meeting an accident. He was known for his pioneer work of identifying the process that how taste and smell are detected and coded in Brain.

About Prof. Obaid Siddiqui:
  • Born in 1932 in UP, received his education at Aligarh Muslim University.
  • He did his Ph.D. from University of Glasgow, where he worked on microbial genetics with Harbor Pontecorvo.
  • He was the National Research Professor at the National Centre for Biological Sciences, Tata Institute of Fundamental Research, in Bangalore.
  • In 1961, Siddiqi and Alan Garen discovered suppressor of nonsense mutations in the gene for alkaline phosphatase. This work led to the elucidation of the stop codons in the genetic code and the mechanism of chain termination during protein synthesis.
What are Stop Codons?

In the genetic code, a Stop Codon (or Termination Codon) is a nucleotide triplet within messenger RNA that signals a termination of translation. Proteins are based on polypeptides, which are unique sequences of amino acids. Most codons in messenger RNA (from DNA) correspond to the addition of an amino acid to a growing polypeptide chain, which may ultimately become a protein. Stop codons signal the termination of this process by binding release factors, which cause the ribosomal subunits to disassociate, releasing the amino acid chain.

In the standard genetic code, there are several stop codons:


  • UAG (“amber”)
  • UAA (“ochre”)
  • UGA (“opal”)


  • TAG (“amber”)
  • TAA (“ochre”)
  • TGA (“opal” or “umber”)