6.4 Translation

• RNA to Polypeptide Chain is the process of synthesizing a polypeptide from genetic information encoded in RNA
• This process occurs on ribosomes, which are complex molecular machines made up of proteins and RNA
• In eukaryotic cells, ribosomes are found floating freely in the cytoplasm
• A significant portion of protein synthesis in eukaryotic cells also occurs on the rough endoplasmic reticulum (RER)
• During translation, the mRNA is first bound to the ribosome and then read in groups of three nucleotides called codons
• Each codon specifies a specific amino acid, and the ribosome adds the corresponding amino acid to the growing polypeptide chain
• Protein synthesis begins in the nucleus, where mRNA is transcribed from DNA
• The mRNA then moves to the cytoplasm, where it is translated into a protein
• In prokaryotic organisms, transcription and translation occur simultaneously
• This simultaneous transcription and translation process in prokaryotes is known as coupled transcription-translation
• The three main steps of translation are initiation, elongation, and termination
• Initiation involves the binding of a specific initiator tRNA and the small and large ribosomal subunit to the mRNA
• Elongation involves the addition of amino acids to the growing polypeptide chain by tRNAs carrying specific amino acids
• Termination involves the release of the polypeptide from the ribosome when a stop codon is reached
• The genetic code is the set of rules by which the sequence of nucleotides in DNA and RNA is translated into the sequence of amino acids in proteins
• Nearly all living organisms use the same genetic code, indicating a common ancestry
• tRNA brings the correct amino acid to the correct place specified by the codon on the mRNA
• Retroviruses use RNA as the genetic material and replicate through reverse transcription
• Reverse transcription is catalyzed by an enzyme called reverse transcriptase, which converts viral RNA into DNA
• The ability of retroviruses to integrate into the host genome can lead to long-term viral persistence and the development of viral-associated diseases