Question

“Prediction of the sequence of amino acids from the nucleotide sequence in mRNA is very easy, but the exact prediction of the nucleotide sequence in mRNA from the sequence of amino acids coded by mRNA is difficult”. Which properties of the genetic code is the reason for the above condition? Explain.

Answer 1

Hint: Amino acids are a set of 20 different protein-building molecules used. The amino acid chain's sequence allows the polypeptide to fold into a biologically active form. Protein amino acid sequences are encoded in genes.

Complete answer: Translation is the mechanism in which proteins are synthesized by ribosomes in the cytoplasm or endoplasmic reticulum after the DNA to RNA transcription process in the nucleus of the cell. The whole system is called gene expression. In translation, to generate a particular amino acid chain or polypeptide, messenger RNA (mRNA) is decoded in a ribosome, outside the nucleus. Later, the polypeptide folds into an active protein and in the cell performs its functions. By inducing the binding of complementary tRNA anticodon sequences to mRNA codons, the ribosome facilitates decoding. When the mRNA goes through and is "read" by the ribosome, the tRNAs bring unique amino acids that are chained together into a polypeptide. The instructions for constructing a polypeptide are in groups of three nucleotides called codons in an mRNA. These relationships are known to us. There is a degeneration of the genetic code. More than one codon is available that can code for the same amino acids. The nucleotide sequence that is present on the mRNA is also difficult to trace with the aid of the amino acid sequence. Therefore degeneracy is the property of genetic code which lacks to predict the exact nucleotide sequence in mRNA.

Note: One of the properties of genetic code is that it is universal in nature. Genetic codes are unambiguous which means each codon codes for only one amino acid. Most of the amino acids available in nature can be coded by more than one codon. This characteristic of genetic code is called redundancy.