Which of the following processes occurs during transcription?
A. RNA is synthesized
B. DNA is synthesized
C. Proteins are synthesized mRNA attaches to ribosomes
D. All of the above are true
The Correct Answer and Explanation is:
The correct answer is A. RNA is synthesized.
Explanation:
Transcription is the first step of gene expression, where the genetic information stored in DNA is copied into a messenger RNA (mRNA) molecule. This process occurs in the nucleus of eukaryotic cells and involves the synthesis of RNA, which will later be translated into proteins. Let’s break down the options:
- A. RNA is synthesized: This is the correct statement. During transcription, RNA is synthesized by RNA polymerase, an enzyme that reads the DNA sequence of a gene and synthesizes a complementary strand of RNA. This RNA is usually mRNA, but it can also be other types of RNA (e.g., tRNA, rRNA) depending on the gene being transcribed. The mRNA carries the genetic instructions from the DNA to the ribosomes in the cytoplasm, where translation occurs to form proteins.
- B. DNA is synthesized: This is incorrect in the context of transcription. DNA synthesis occurs during DNA replication, not transcription. In replication, DNA is duplicated to ensure that each daughter cell receives an exact copy of the genetic material during cell division.
- C. Proteins are synthesized: This is incorrect for transcription. Proteins are synthesized during translation, not transcription. Translation is the process where mRNA is used as a template to create a polypeptide chain, which will fold into a functional protein. Transcription only involves the creation of the RNA transcript from the DNA template.
- D. mRNA attaches to ribosomes: This happens after transcription, not during it. Once the mRNA is synthesized in the nucleus, it moves to the cytoplasm, where it attaches to ribosomes to be translated into a protein. This process is part of translation, not transcription.
Conclusion:
Transcription is solely concerned with the synthesis of RNA (specifically mRNA in most cases). DNA is used as a template to create a complementary RNA strand, which is then processed and transported out of the nucleus for translation into proteins.