Transcription

Definition

Transcription is the process by which the information encoded in a gene's DNA is copied into messenger RNA (mRNA). This essential step in gene expression allows for the transfer of genetic information from the stable DNA in the nucleus to the more versatile mRNA, which can then be translated into proteins. Transcription occurs in the cell nucleus and is a vital part of the central dogma of molecular biology, bridging the gap between the genetic blueprint and functional proteins.

5 Must Know Facts For Your Next Test

1. Transcription begins at specific sites on the DNA called promoters, where RNA polymerase binds to initiate the synthesis of mRNA.
2. During transcription, the DNA double helix unwinds and one strand serves as a template to guide the synthesis of complementary RNA.
3. Transcription involves three main steps: initiation, elongation, and termination, each crucial for producing a correct mRNA strand.
4. The resulting mRNA undergoes processing, including capping, polyadenylation, and splicing, before it can be translated into a protein.
5. In eukaryotic cells, transcription occurs in the nucleus, while translation occurs in the cytoplasm, highlighting the separation of these processes.

Review Questions

• How does transcription differ between prokaryotic and eukaryotic cells?
  • Transcription in prokaryotic cells occurs in the cytoplasm since they lack a defined nucleus, and it often happens simultaneously with translation. In contrast, eukaryotic transcription takes place in the nucleus, where mRNA is synthesized and then processed before being transported to the cytoplasm for translation. Additionally, eukaryotic transcription involves more complex regulatory mechanisms and post-transcriptional modifications than prokaryotic transcription.
• Discuss the role of RNA polymerase in transcription and how it influences gene expression.
  • RNA polymerase plays a critical role in transcription by binding to the promoter region of a gene and catalyzing the synthesis of mRNA from the DNA template. The activity and efficiency of RNA polymerase can significantly influence gene expression; factors such as transcription factors can enhance or inhibit its activity, thereby regulating how much mRNA is produced. This regulation affects overall protein synthesis and ultimately impacts cellular functions and responses.
• Evaluate how mutations in DNA can affect transcription and potentially lead to disease.
  • Mutations in DNA can significantly impact transcription by altering promoter regions or other regulatory sequences that control RNA polymerase binding and activity. For example, mutations that disrupt binding sites can lead to insufficient or absent mRNA production for essential genes, resulting in reduced protein levels or dysfunctional proteins. Such disruptions can contribute to various diseases, including cancer and genetic disorders, highlighting the importance of precise transcriptional regulation for maintaining healthy cellular function.

Related terms

RNA Polymerase: An enzyme responsible for synthesizing RNA from a DNA template during the process of transcription.

mRNA: Messenger RNA, a type of RNA that carries the genetic information from DNA to the ribosome for protein synthesis.

Promoter: A specific DNA sequence that serves as a binding site for RNA polymerase to initiate transcription.