List/explain the steps of the protein synthesis process

Answer 1

The process of protein synthesis is divided into two main steps: transcription and translation. Here are the steps explained:

1. Transcription:
- Initiation: RNA polymerase binds to the promoter region on the DNA molecule. This signals the beginning of transcription.
- Elongation: RNA polymerase moves along the DNA molecule, unwinding it and creating a single-stranded RNA copy. Complementary RNA nucleotides are added according to the base pairing rules (A-U and G-C). This forms the pre-mRNA molecule.
- Termination: Once RNA polymerase reaches the termination signal on the DNA molecule, it dissociates from the DNA, and the pre-mRNA is released.

2. RNA Processing:
- Capping: A protective cap (modified nucleotide) is added to the 5' end of the pre-mRNA molecule. This cap helps in the stability and recognition of the mRNA.
- Polyadenylation: A poly-A tail (string of adenine nucleotides) is added to the 3' end of the mRNA. This tail also contributes to the stability of the mRNA.
- Splicing: Introns (non-coding regions) are removed from the pre-mRNA molecule, leaving only exons (coding regions). This process is carried out by spliceosomes, which consist of snRNPs (small nuclear ribonucleoproteins).

3. Translation:
- Initiation: The mRNA attaches to a ribosome, and the ribosome moves along the mRNA until it reaches the start codon (AUG). This signals the initiation of translation. tRNA molecules, carrying amino acids, enter the ribosome.
- Elongation: The ribosome reads the mRNA codons in sets of three (codon) and pairs them with the corresponding tRNA molecules carrying specific amino acids. The ribosome then joins the amino acids together, forming a polypeptide chain.
- Termination: The ribosome reaches a stop codon (UAA, UAG, or UGA) on the mRNA, which signals the end of translation. The newly formed polypeptide chain is released from the ribosome.
- Post-translation modifications: The polypeptide chain may undergo various modifications, such as folding, cleavage, addition of prosthetic groups, or attachment of sugar molecules. These modifications are important for its functional form.

In summary, transcription converts DNA into mRNA, RNA processing modifies the pre-mRNA into mature mRNA, and translation uses the mRNA to synthesize the corresponding protein.