In the central dogma of molecular biology, which process occurs just before protein synthesis at the ribosome by producing the messenger RNA that will be translated?

Introduction / Context:
The central dogma of molecular biology describes the flow of genetic information from DNA to RNA to protein. Proteins are synthesised at ribosomes during a process called translation, and this process requires a messenger RNA template. This question asks which process immediately precedes protein synthesis at the ribosome by generating that messenger RNA.

Given Data / Assumptions:

• We are considering events leading up to protein synthesis at ribosomes.
• The options include transcription, replication, translation itself, and chromosome duplication.
• We assume knowledge that mRNA must be made before it can be translated.

Concept / Approach:
Transcription is the process in which a segment of DNA is used as a template to synthesise RNA, specifically messenger RNA for protein coding genes. This mRNA carries the genetic code from the nucleus to the ribosome. Translation is the process that uses the codon sequence in mRNA to assemble amino acids into a polypeptide chain. Replication and chromosome duplication refer to copying DNA for cell division, not to creating RNA for protein synthesis. Therefore, the process that immediately precedes translation at the ribosome is transcription.

Step-by-Step Solution:
Step 1: Recall the order of information flow: DNA → RNA → protein. Step 2: Recognise that transcription is the step in which DNA is copied into RNA, producing messenger RNA. Step 3: Understand that translation is the step that occurs at ribosomes, where the mRNA code is used to assemble a protein. Step 4: Conclude that the process just before protein synthesis at the ribosome is transcription, because it produces the mRNA needed for translation.

Verification / Alternative check:
Standard diagrams of gene expression show a gene in DNA being transcribed by RNA polymerase to form pre mRNA, which is processed into mature mRNA. This mRNA then exits the nucleus and binds to a ribosome, where translation synthesises the protein. Replication is shown separately as part of cell division. These diagrams confirm that transcription precedes translation in the sequence of events leading to protein synthesis.

Why Other Options Are Wrong:

• Replication: This is the process of copying the entire DNA molecule before cell division and does not directly produce the mRNA used at the ribosome.
• Translation: Translation is the protein synthesis step itself, not the process that comes before it.
• Duplication of the entire chromosome set: This is another way of describing replication, which is not the immediate step before protein synthesis.

Common Pitfalls:
Students sometimes confuse transcription and translation because both involve copying information. A helpful memory aid is that “transcription” is like copying a text from one script to another (DNA to RNA), while “translation” converts the nucleotide language into the amino acid language. Remembering that transcription produces mRNA and translation uses that mRNA at the ribosome helps to keep the sequence clear.

Final Answer:
The process that immediately precedes protein synthesis at the ribosome is transcription, which produces the mRNA that will be translated.