Final answer:
The molecule in the central dogma that is comparable to a disposable photocopy is messenger RNA (mRNA), as it serves as a temporary copy of genetic information for protein synthesis.
Step-by-step explanation:
Understanding the Central Dogma of Molecular Biology
The central dogma of molecular biology states that genetic information flows from DNA to RNA (in this case, messenger RNA or mRNA) and then to Protein. This sequence of information transfer is critical for cellular function, and each molecule involved plays a specific role in the process.
Roles of DNA, RNA, and Protein
DNA is the keeper of the genetic code, the original blueprint for all cellular proteins; it remains safely in the nucleus. RNA acts as a middleman in this process. Among the types of RNA, mRNA is the most similar to the 'disposable photocopy' in our analogy because it acts as a temporary copy of a gene that determines the sequence of amino acids in proteins.
In contrast, tRNA carries amino acids to the ribosome for protein synthesis, and rRNA is a major constituent of ribosomes themselves. The process of copying DNA information into RNA is known as transcription, and using that RNA to make a protein is known as translation.
Why mRNA is the 'Disposable Photocopy'
French scientists François Jacob and Jacques Monod suggested the existence of an intermediary molecule, which was identified as mRNA. This molecule temporarily carries the genetic information needed to synthesize proteins. It is this temporary and disposable nature of mRNA that makes it akin to a photocopy of a specific part of the DNA needed at a given time—just as a student might make a photocopy of a few pages of a library book rather than checking out the entire book.
In summary, the molecule that resembles a 'disposable photocopy' in the central dogma is (b) mRNA. It is created as a single-stranded copy of the DNA during transcription, carrying the instructions for protein synthesis to the ribosome where translation into a protein occurs.