The diagram above shows the difference in the synthesis of in normal DNA and abnormal DNA. The top strand shows the normal DNA, mRNA and amino acid sequences. A single substitution mutation has changed the base sequence in the DNA. The base sequence on the mRNA produced by the DNA is altered. As a result, a codon on the mRNA is altered. A different amino acid is inserted into the protein chain. The amino acid valine is inserted instead of glutamic acid, which is shown by the bottom strand of DNA. The protein is altered and no longer functions normally. These sequences result in sickle-shaped red blood cells. This blood disorder is known as sickle cell anaemia.
The amino acids are joined to form proteins by peptide bonds. The formation of peptide bonds requires a good amount of energy. Therefore, in the first phase of translation for protein synthesis, the amino acids are activated in the presence of ATP and linked to their cognate tRNA (transfer RNA). This process is called as charging of the tRNA or aminoacylation of tRNA. If two such charged tRNA are brought close enough, the formation of peptide bond between them is favored energetically. This function occurs inside the , as it contains two sites for subsequent amino acids to bind to and thus be close enough for bonding.
All steps of protein synthesis easily explained, ..
The process of polymerization of amino acids to form a polypeptide is called as Translation. It is the second and final step of protein synthesis. The order into which the amino acids are arranged is defined by the bases in mRNA (messenger). Ribosome is the cellular factory responsible for the protein synthesis. The ribosome consists of structural RNAs and about 80 different . It is in inactive stage and exists as two subunits, one large and other small. The synthesis of begins when the small subunit encounters an mRNA. The ribosome also acts as a catalyst for the formation of bonds.