DNA and RNA - Transcription

Introduction

This tutorial explains the process of transcription, which is the first step in synthesizing proteins from the genetic code in DNA. Understanding transcription is vital for grasping how proteins are built in cells, making it a cornerstone of molecular biology.

Step 1: Understanding Transcription

• Transcription is distinct from DNA replication and cell division processes like mitosis.
• Its primary function is to convert DNA's genetic code into messenger RNA (mRNA), which carries the instructions to synthesize proteins outside the nucleus.

Step 2: Role of RNA Polymerase

• The enzyme RNA polymerase initiates transcription by attaching to a specific segment of DNA known as a gene.
• A gene contains the code for a specific protein, represented by a sequence of three nitrogenous bases called a codon, each coding for an amino acid.

Step 3: Unwinding the DNA

• RNA polymerase causes the DNA helix to unwind, separating it into two strands:
  • Template Strand: The strand that is read by RNA polymerase to create RNA.
  • Non-Template Strand: The strand that is not transcribed.

Step 4: Synthesizing Messenger RNA

• Using the template strand as a guide, RNA polymerase assembles free nucleotides into a complementary RNA strand following the base pair rule:
  • Thymine (T) on DNA pairs with Adenine (A) on RNA.
  • Adenine (A) on DNA pairs with Uracil (U) on RNA (not thymine).
  • Cytosine (C) pairs with Guanine (G), and Guanine (G) pairs with Cytosine (C).

Step 5: Completing the Transcription Process

• Once transcription is complete, the newly formed mRNA strand is small enough to exit the nucleus through a nuclear pore.
• This mRNA will then travel to the ribosome, where protein synthesis occurs in a subsequent process called translation.

Conclusion

Transcription is a critical step in protein synthesis, where the genetic information from DNA is transcribed into mRNA. Key takeaways include understanding the role of RNA polymerase, the distinction between the template and non-template strands, and the base pairing rules that guide mRNA synthesis. For further learning, explore the translation process to see how proteins are built from the mRNA created during transcription.