Transcription and Translation

Transcription

Transcription is the first step in protein synthesis where the DNA sequence of a gene is copied into messenger RNA (mRNA).
It occurs in the nucleus in eukaryotes and the cytoplasm in prokaryotes.
This process is catalysed by RNA polymerase, an enzyme that unwinds the DNA and synthesizes the RNA transcript.
Transcription elicits three main stages: initiation, elongation, and termination.
During transcription, only one DNA strand (template strand) is used to synthesise mRNA.
Transcription results in the replacement of the thymine (T) base in DNA with uracil (U) in mRNA.

Translation is the process that interprets the genetic information in mRNA to synthesise a protein.
This process occurs in the cytoplasm, specifically on the ribosomes.
Every three nucleotides on the mRNA form a codon, which corresponds to a specific amino acid.
The order of these codons determines the sequence of amino acids in the resulting protein.
Transfer RNAs (tRNAs) carry corresponding amino acids to the ribosome, based on the sequence of codons in the mRNA.
The amino acids are then joined together by peptide bonds in a process called peptide bond formation.
The chain of amino acids (polypeptide) continues to grow until a stop codon is reached, signalling the end of translation.

After translation, many proteins undergo post-translational modifications to become fully functional.
This can include the addition of functional groups, cleavage of certain amino acids, or formation of disulphide bridges.
Proteins could also fold into their specific 3D structures, crucial for their function.
Some proteins require the addition of other chemical groups (like phosphates or carbohydrates) as part of their maturation process.
These modifications enhance the diversity of the protein functions that can be derived from the genetic code.