Transcription

Definition

Transcription is the process by which the genetic information encoded in DNA is copied into messenger RNA (mRNA), which serves as a template for protein synthesis. This process is crucial because it allows the genetic code to be expressed and ultimately translated into proteins that carry out various functions in the cell. Understanding transcription connects to the structure and types of RNA involved, the cellular organelles responsible for facilitating this process, and the central dogma of molecular biology that outlines how genetic information flows within biological systems.

5 Must Know Facts For Your Next Test

1. Transcription occurs in the nucleus of eukaryotic cells, where DNA is located, and involves several steps: initiation, elongation, and termination.
2. During transcription, RNA polymerase binds to a specific region of DNA called the promoter, marking the beginning of the gene to be transcribed.
3. The newly formed mRNA molecule is complementary to the DNA template strand, with uracil (U) replacing thymine (T).
4. In eukaryotes, pre-mRNA undergoes processing, which includes the addition of a 5' cap, poly-A tail, and splicing to remove introns before becoming mature mRNA.
5. Transcription factors are proteins that help regulate the transcription process by assisting RNA polymerase in binding to DNA and initiating transcription.

Review Questions

• How does the structure of RNA contribute to its role in transcription?
  • The structure of RNA is single-stranded and consists of nucleotides that include ribose sugar, phosphate groups, and nitrogenous bases. This single-stranded nature allows RNA to fold into various shapes, which is essential for its functions in transcription and later during translation. The base pairing rules between RNA and DNA also play a critical role in ensuring that RNA accurately reflects the genetic code found in DNA during transcription.
• Discuss the role of RNA polymerase and transcription factors in initiating transcription.
  • RNA polymerase is the key enzyme that synthesizes mRNA from a DNA template during transcription. Transcription factors are proteins that bind to specific DNA sequences near the promoter region of a gene, facilitating RNA polymerase's attachment to DNA. Together, these components ensure accurate and regulated transcription initiation, allowing cells to respond to internal and external signals effectively.
• Evaluate the significance of mRNA processing after transcription and its impact on gene expression.
  • After transcription, mRNA undergoes processing steps such as capping, polyadenylation, and splicing. These modifications are crucial as they enhance mRNA stability, facilitate its export from the nucleus to the cytoplasm, and prevent degradation. Properly processed mRNA ensures that only the coding regions (exons) are translated into proteins, thus playing a vital role in gene expression regulation. Any errors in this processing can lead to dysfunctional proteins and contribute to various diseases.

Related terms

mRNA:

Messenger RNA is a type of RNA that carries genetic information from DNA to the ribosome, where proteins are synthesized.

RNA polymerase: An enzyme that synthesizes RNA from a DNA template during the process of transcription.

introns: Non-coding sequences in a gene that are transcribed into pre-mRNA but are removed during RNA splicing before translation.