Lecture G9 (Transcription)

What is the role of transcription in gene expression?

Transcription converts genetic information in DNA into RNA, which can then be translated into protein

Where does transcription occur in eukaryotic cells?

In the nucleus

What is the product of transcription?

Messenger RNA (mRNA), which carries the genetic code from DNA to the ribosome

What enzyme synthesizes RNA?

RNA polymerase II

Does RNA polymerase need a primer?

No, it can start synthesis on its own

What is the role of transcription factors?

They help RNA polymerase bind to the promoter and start transcription

What is the transcription initiation complex?

The full assembly of RNA polymerase II and transcription factors bound to the promoter

What is a promoter

A DNA sequence where RNA polymerase and transcription factors bind to start transcription

What is the TATA box?

A common promoter sequence that helps position RNA polymerase II correctly

What is RNA processing?

The modification of pre-mRNA into mature mRNA before it leaves the nucleus

What are the three main steps in RNA processing?

1. Addition of a 5’ cap

2. Addition of a 3’ poly-A tail

3. Removal of introns (RNA splicing)

Introns

Non-coding regions removed from pre-mRNA

Exons

Coding regions that remain and are expressed

What is the function of the 5’ cap and 3’ poly-A tail?

They protect mRNA from degradation, aid in export from the nucleus, and help ribosome binding

Why can eukaryotes produce more proteins than they have genes?

Because of alternative RNA splicing, where different exons are combined to produce multiple mRNA variants from a single gene

What is the benefit of alternative RNA splicing?

It increases protein diversity without increasing the number of genes