Lecture Notes: Transcription and Translation in Cells

Overview

Understanding transcription and translation is key to comprehending how DNA information is converted into proteins, the building blocks of cells and enzymes.
The lecture emphasized differences in transcription between eukaryotic and prokaryotic cells.

Eukaryotic Cells:
- Eukaryotic messenger RNA (mRNA) undergoes processing to remove introns (non-coding regions).
- This processing involves splicing out introns, making eukaryotic transcription more complex.
Prokaryotic Cells:
- Prokaryotic cells (bacteria) lack introns, making transcription simpler compared to eukaryotes.

RNA Characteristics:
- Contains uracil (U) instead of thymine (T) found in DNA.
- Has ribosugars in the backbone instead of deoxyribosugars.
DNA Characteristics:
- DNA consists of coding genes and regulatory regions such as promoters.

Key Terms:
- Promoter: DNA region where RNA polymerase binds to start mRNA synthesis.
- Terminator: DNA sequence where RNA polymerase stops mRNA synthesis and detaches.
Process of Transcription:
- Initiation: RNA polymerase binds to promoter and begins unwinding DNA.
- Elongation: mRNA is synthesized by adding complementary RNA bases to the template DNA strand.
  - Complementary base pairing: C-G, A-U, G-C, T-A in the template strand.
- Termination: RNA polymerase encounters the terminator sequence and stops mRNA synthesis.

Illustrations depict RNA polymerase opening a small DNA bubble to synthesize mRNA.
Template Strand: Used by RNA polymerase to build complementary mRNA.
Coding/Non-template Strand: Matches the mRNA sequence (except U replaces T).
Direction of mRNA synthesis: 5' to 3'.

Multiple mRNA copies can be synthesized from a single gene, making DNA reusable.
Eukaryotic transcription involves additional features like TATA boxes, methyl G caps, and poly-A tails, which were not crucial for this discussion.
An animation video illustrating transcription in eukaryotic cells was recommended for visualization despite the additional complexity.