Transcription is the biological process of copying a segment of DNA into RNA, specifically messenger RNA (mRNA), which carries the genetic information needed to produce proteins. This process occurs when a gene needs to be expressed, meaning when the cell requires the protein encoded by that gene
. Key points about transcription:
- It involves making an RNA copy of a gene's DNA sequence. The RNA produced is complementary to the DNA template strand but uses uracil (U) instead of thymine (T)
- Only one strand of the DNA, called the template strand, is transcribed by the enzyme RNA polymerase, which reads the DNA from 3' to 5' and synthesizes RNA in the 5' to 3' direction
- The resulting mRNA is a single-stranded molecule that carries the genetic code from the nucleus (where DNA resides) to the cytoplasm, where proteins are synthesized
- In eukaryotic cells, the initial RNA transcript (pre-mRNA) undergoes processing (splicing and modification) to become mature mRNA before it exits the nucleus
- Transcription is the first step in gene expression, followed by translation, where the mRNA code is used to build proteins
In summary, transcription is the process by which the genetic code stored in DNA is transcribed into an RNA copy (mRNA), enabling the cell to produce specific proteins as needed
