Key Points for Transcription

Transcription

• Definition: Transcription is the process of copying genetic information from DNA to RNA.
• Location: It occurs in the nucleus of eukaryotic cells.

Eukaryotic Chromosomes

• Eukaryotic chromosomes are thread-like structures found in the nucleus.
• They contain genetic information in the form of DNA.
• Eukaryotes have multiple linear chromosomes.

RNA Polymerase

• RNA polymerase is an enzyme responsible for transcription.
• It binds to the promoter region of DNA.
• It synthesizes an RNA molecule complementary to the DNA template strand.
• RNA polymerase III catalize transcription of tRNA, 5 srRNA and snRNA.

Promoter of Protein-Coding Region DNA

• The promoter is a specific DNA sequence.
• It is located upstream (towards the 5’ end) of the gene’s coding region.
• It’s the recognition site for RNA polymerase and transcription factors.

Transcription Initiation

• It’s the first step of transcription.
• RNA polymerase binds to the promoter region.
• It initiates unwinding of the DNA double helix.

Production of Mature mRNA

• After transcription, pre-mRNA undergoes processing:
  1. Capping: Addition of a 7-methylguanosine cap at the 5’ end.
  2. Polyadenylation: Addition of a poly-A tail at the 3’ end.
  3. Splicing: Removal of introns and joining of exons.

Steps of Pre-mRNA Processing

• Pre-mRNA processing includes capping, polyadenylation, and splicing.
• These steps are crucial for producing functional mature mRNA.

Expressed Sequence Tags

• Expressed Sequence Tags or ESTs are genes that are expressed as RNA in the body. ESTs represent portions of expressed genes. They may be represented as either cDNA/mRNA sequence or as the reverse complement of the mRNA, the template strand.