Genetic basis of inheritance 12th pdf

Each codon consists of three nucleotides, usually corresponding to a single amino acid. The nucleotides are abbreviated with the letters A, U, G genetic basis of inheritance 12th pdf C. This mRNA molecule will instruct a ribosome to synthesize a protein according to this code.


RNA three nucleotides at a time. The genetic code is highly similar among all organisms and can be expressed in a simple table with 64 entries.

The code defines how sequences of nucleotide triplets, called codons, specify which amino acid will be added next during protein synthesis. With some exceptions, a three-nucleotide codon in a nucleic acid sequence specifies a single amino acid. While the “genetic code” determines a protein’s amino acid sequence, other genomic regions determine when and where these proteins are produced according to various “gene regulatory codes”. Efforts to understand how proteins are encoded began after DNA’s structure was discovered in 1953.

The Crick, Brenner et al. Marshall Nirenberg and Heinrich J. Matthaei were the first to reveal the nature of a codon in 1961.

They thereby deduced that the codon UUU specified the amino acid phenylalanine. Therefore, the codon AAA specified the amino acid lysine, and the codon CCC specified the amino acid proline. Using various copolymers most of the remaining codons were then determined. Subsequent work by Har Gobind Khorana identified the rest of the genetic code.

This work was based upon Ochoa’s earlier studies, yielding the latter the Nobel Prize in Physiology or Medicine in 1959 for work on the enzymology of RNA synthesis. Extending this work, Nirenberg and Philip Leder revealed the code’s triplet nature and deciphered its codons. In these experiments, various combinations of mRNA were passed through a filter that contained ribosomes, the components of cells that translate RNA into protein.

Unique triplets promoted the binding of specific tRNAs to the ribosome. Leder and Nirenberg were able to determine the sequences of 54 out of 64 codons in their experiments. Khorana, Holley and Nirenberg received the 1968 Nobel for their work.

The three stop codons were named by discoverers Richard Epstein and Charles Steinberg. Amber” was named after their friend Harris Bernstein, whose last name means “amber” in German.

The other two stop codons were named “ochre” and “opal” in order to keep the “color names” theme. RNA-synthetase pair to encode it with diverse physicochemical and biological properties in order to be used as a tool to exploring protein structure and function or to create novel or enhanced proteins.

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