RNA Notes

Chapter 13 Notes: RNA

Overview of RNA

• Ribonucleic Acid (RNA): A single-stranded nucleic acid involved in protein synthesis.
• Key Differences from DNA:
  • Sugar: RNA contains ribose, while DNA contains deoxyribose.
  • Strand Structure: RNA is typically single-stranded, whereas DNA is double-stranded.
  • Nucleobases: RNA contains uracil (U) instead of thymine (T) found in DNA.

Functions of RNA

• Main Role: RNA is essential in synthesizing proteins by carrying instructions from DNA.
• Gene: A segment of DNA that contains the instructions coding for a protein.

Types of RNA

1. Messenger RNA (mRNA):

   • Functions as a messenger carrying genetic information from the nucleus to the cytoplasm for protein synthesis.
   • Carries the code for amino acid sequences.

2. Ribosomal RNA (rRNA):

   • A structural component of ribosomes, which are the sites of protein synthesis in the cell.
   • Combines with proteins to form ribosomes, facilitating translation.

3. Transfer RNA (tRNA):

   • Transfers specific amino acids to the ribosome during protein synthesis.
   • Each tRNA molecule is associated with a specific amino acid and matches with mRNA codons.

The Process of Protein Synthesis

• Transcription: The first step in protein synthesis that occurs in the nucleus.
  • Involves copying part of the DNA sequence to create a complementary strand of mRNA.
  • RNA Polymerase: The enzyme responsible for synthesizing RNA from the DNA template by unwinding the DNA and assembling the RNA strand.
  • Base Pairing: In RNA, adenine (A) pairs with uracil (U), and cytosine (C) pairs with guanine (G).
  • Example: For a DNA sequence running (3’ to 5’) - A T G C, the corresponding mRNA will be (5’ to 3’) - U A C G.

Key Terminology

• Nontemplate Strand: The DNA strand that is not used for transcription; it has the same sequence as the mRNA (excluding T, which is replaced by U).
• Template Strand: The DNA strand used by RNA polymerase to produce mRNA.
• Direction of Transcription: RNA is synthesized in the 5’ to 3’ direction.

Summary

• RNA plays a crucial role in translating genetic information into actionable protein synthesis by acting as a message, a structural component, and a transporter within the cell. Its unique structure and various types allow it to fulfill its roles effectively in the cellular machinery.