Central dogma

Definition

The central dogma is a fundamental principle in molecular biology that describes the flow of genetic information within a biological system. It explains how DNA is transcribed into RNA, which is then translated into proteins, the functional molecules that carry out most cellular processes. This concept highlights the unidirectional transfer of genetic information and is essential for understanding how genes control cellular functions and traits.

5 Must Know Facts For Your Next Test

1. The central dogma was first articulated by Francis Crick in 1957, emphasizing the directional flow of genetic information.
2. During transcription, RNA polymerase binds to the promoter region of a gene, unwinding the DNA to synthesize a complementary RNA strand.
3. The mRNA produced during transcription undergoes processing, including 5' capping and polyadenylation, before it can be translated into protein.
4. Translation occurs at ribosomes, where transfer RNA (tRNA) molecules bring amino acids that correspond to the codons on the mRNA strand.
5. While the central dogma outlines a straightforward pathway, exceptions exist, such as reverse transcription in retroviruses, which convert RNA back to DNA.

Review Questions

• How does transcription fit into the central dogma and what role does RNA polymerase play in this process?
  • Transcription is the first step in the central dogma where DNA is converted into RNA. RNA polymerase is crucial in this process as it binds to the promoter region of a gene and unwinds the DNA to synthesize a complementary strand of RNA. This RNA serves as the messenger that carries genetic information from DNA to the ribosomes for protein synthesis.
• Discuss the significance of mRNA processing in relation to the central dogma and its impact on gene expression.
  • mRNA processing is significant because it ensures that the mRNA molecule is mature and functional before it leaves the nucleus for translation. This processing includes adding a 5' cap and a poly-A tail, as well as splicing out introns. These modifications enhance mRNA stability and translational efficiency, thereby playing a crucial role in regulating gene expression and ensuring accurate protein synthesis.
• Evaluate how exceptions to the central dogma, such as reverse transcription, challenge traditional views of genetic information flow.
  • Exceptions like reverse transcription challenge traditional views by demonstrating that genetic information can flow in reverse—from RNA back to DNA. This occurs in retroviruses like HIV, which utilize reverse transcriptase to convert their RNA genome into DNA after infecting a host cell. This ability complicates our understanding of genetic information flow and illustrates the complexity of molecular biology beyond the classic central dogma framework.

Related terms

Transcription: The process by which the information in a segment of DNA is copied into messenger RNA (mRNA) as the first step of gene expression.

Translation: The process by which the sequence of nucleotides in mRNA is decoded to produce a specific sequence of amino acids, forming a protein.

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