A researcher develops a new drug that kills cells by preventing transcription. The most direct effect of the drug is to prevent cells from? A. making new DNA. B. exporting substances to the cytoplasm. C. making protein. D. breaking down substances in the cytoplasm.
To determine the most direct effect of the drug that prevents transcription, we need to understand the process of transcription and its role in cell function.
During transcription, the genetic information stored in DNA is converted into RNA molecules. This process takes place within the cell's nucleus and involves an enzyme called RNA polymerase that binds to the DNA and produces a complementary RNA strand, known as messenger RNA (mRNA). The mRNA molecule carries the instructions from the DNA to the ribosomes, where protein synthesis occurs.
Now, let's evaluate the given options:
A. Making new DNA: The process of making new DNA occurs during DNA replication, not transcription. Transcription is responsible for producing RNA molecules, not DNA molecules. Therefore, preventing transcription would not directly affect the cell's ability to make new DNA. So, option A is incorrect.
B. Exporting substances to the cytoplasm: While transcription occurs in the nucleus, it is primarily responsible for producing mRNA. Exporting substances to the cytoplasm is the role of other cellular processes, such as nuclear export and vesicular transport. Thus, preventing transcription would not directly affect the cell's ability to export substances to the cytoplasm. Therefore, option B is incorrect.
C. Making protein: Transcription is a crucial step in protein synthesis. It produces mRNA molecules that carry the instructions for making proteins. The mRNA is then translated by ribosomes in the cytoplasm, ultimately leading to protein production. If transcription is prevented, the production of mRNA would be disrupted, subsequently hindering the cell's ability to make proteins. Therefore, option C is the correct answer.
D. Breaking down substances in the cytoplasm: The breakdown of substances in the cytoplasm is primarily carried out by cellular processes such as cellular respiration, lysosomal degradation, and other metabolic pathways. Transcription is not directly involved in these processes, so preventing it would not directly affect substance breakdown in the cytoplasm. Therefore, option D is incorrect.
In summary, the most direct effect of the drug that prevents transcription is to prevent cells from making protein (option C).