Transcription
The
genetic information housed in DNA undergoes transcription, leading to the
generation of a single-stranded mRNA. This pivotal process, explored in prior
blog posts, is dubbed transcription. The resulting mRNA, aptly named for its
role in carrying the genetic message from DNA, contains codons mirroring the
DNA's codes.
Translation
This
intricate mechanism involves the translation of mRNA's triplet bases into a
specific sequence of amino acids, constituting a polypeptide chain. The
translation process encompasses essential stages:
Ribosome-MRNA
Binding: mRNA aligns with a 30S ribosome,
followed by the joining of the 50S subunit, culminating in the formation of an
80S ribosome. Within this assembly, distinct sites exist:
A
site (Amino-acyl site)
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| Binding of mRNA with the ribosome |
Amino
Acid Activation: Enzymatic
activation of amino acids occurs via attachment to AMP, inducing higher energy
states. This activation process is catalyzed by activation enzymes, yielding
Enzyme-Amino Acid-AMP+PP.
Amino
Acid-tRNA Attachment: Amino acids form
connections with specific tRNA molecules at the 3' end (A-C-C) through
recognition by the D loop of the tRNA.
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| Amino Acid Activation |
Chain
Initiation: The initiation
codon AUG primes the ribosome. A tRNA carrying methionine binds to the
ribosome's P site, facilitated by the UAC anticodon matching the AUG codon.
Adjacent codons are exposed, allowing tRNA with a matching anticodon to engage
the A site. Subsequent peptide bond formation and methionine tRNA release
ensue.
Chain
Elongation: Ribosomal
movement commences, progressing along mRNA by three nucleotides. Additional
tRNAs, each transporting specific amino acids, align with codons, contributing
to polypeptide growth. Sequential peptide bond formation and the release of
tRNA from the P site continue this elongation process.
Chain
Termination: Recognition of
stop codons (UAA, UAG, UGA) halts amino acid joining, preventing tRNA engagement.
This cessation prompts the release of the polypeptide chain from the ribosome,
culminating in translation completion.
 |
| Chain initiation |
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