Question

Describe the process of transcription and translation, in your own words, starting from the DNA double helix and ending with an amino acid chain.

Answer 1

The DNA is a double stranded helix with opposite polarity from 5’ to 3’ and 3’ to 5’ direction. The DNA helix is opened up with the help of enzyme helicase and semi-conservative replication of DNA takes place in 5’ to 3’ direction on both the parent strands.

Transcription: The daughter DNA strands thus generated carry one half from their parents. These DNA strands then undergo transcription by a cascade of enzymes and utilization of energy. The transcription also takes place in 5’ to 3’ direction similar to DNA replication. The major enzyme involved in transcription is RNA polymerase. This enzymes generates a complementary copy of DNA by transcription on the coding strand of DNA. This copy of mRNA is then utilized for translation of proteins.

Translation: After transcription has completed, the resultant mRNA contains a unique sequence of nucleotides which together in a group of three nucleotides are called a codon. A codon encodes for a specific amino acid which are joined end to end to give rise to a polypeptide by the means of a peptide bond between each amino acid. The major part of translation of these codon to amino acids takes place on the ribosomes over the rough endoplasmic reticulum by the help of tRNA and enzyme tRNA amino actyl synthetase. The first amino acid in this polypeptide is always a methionine encoded by codon AUG. Thenafter, subsequent addition of amino acids takes place based upon their sequence on the parent DNA strand and the mRNA transcribed. As the termination codon arrives (UAA, UAG, UGA), translation stops and polypeptide chain terminates. This releases out the polypeptide amino acid chain which later modifies to give rise to a functional protien.

Thus, the processes of transcription and translation give rise to a linear chain of amino acids starting from simple sequences of nucleotide bases.