Transcription part 1

Question 1

What is the central dogma of molecular biology?

Answer 1

DNA → RNA → Protein.

Question 2

What role does mRNA play in the central dogma?

Answer 2

mRNA is a copy of a gene on the DNA, which leaves the nucleus and is read by ribosomes to assemble proteins.

Question 3

What are introns and exons?

Answer 3

Introns: Non-coding regions in a gene; they interrupt exons and are removed during RNA splicing.
Exons: Coding regions that encode protein sequences and remain in the final mRNA.

Question 4

How do introns compare in length to exons?

Answer 4

Introns are generally longer than exons, ranging from 50 to over 100 base pairs.

Question 5

What is transcription?

Answer 5

The process where RNA polymerase synthesizes RNA from a DNA template via complementary base pairing.

Question 6

What are the three stages of transcription?

Answer 6

Initiation: RNA polymerase binds to the promoter.
Elongation: RNA polymerase synthesizes RNA in the 5’ to 3’ direction.
Termination: RNA synthesis stops, and RNA is released.

Question 7

What energy drives RNA synthesis during elongation?

Answer 7

Hydrolysis of ribonucleotide triphosphates (rNTPs) provides the energy.

Question 8

How does transcription initiation differ in prokaryotes and eukaryotes?

Answer 8

Prokaryotes: Sigma factors bind first, recruiting RNA polymerase.
Eukaryotes: General transcription factors (e.g., TBP) bind first, forming the pre-initiation complex with RNA polymerase II.

Question 9

What is a promoter, and where is it located?

Answer 9

A DNA sequence upstream of a gene where RNA polymerase binds to start transcription, typically 25–90 nucleotides from the transcription start site.

Question 10

What happens during RNA splicing?

Answer 10

Introns are removed, and exons are joined to form mature mRNA.

Question 11

What is the significance of RNA splicing?

Answer 11

It ensures only coding sequences (exons) are translated into proteins.

Question 12

At what stages can gene expression be regulated in eukaryotes?

Answer 12

Pre-initiation of transcription.
RNA splicing.
Translation.
Through microRNAs and non-coding RNAs.

Question 13

How is gene expression regulated in prokaryotes?

Answer 13

Primarily at the transcription initiation stage.

Question 14

What is the nucleosome?

Answer 14

A structural unit of chromatin, consisting of DNA wrapped around histone proteins.

Question 15

What is the histone code?

Answer 15

A set of histone modifications (e.g., phosphorylation, acetylation) that regulate gene expression by altering chromatin structure.

Question 16

What are transcription factors?

Answer 16

Proteins that bind DNA at specific sequences to regulate transcription initiation.

Question 17

What is the function of the mediator complex in transcription?

Answer 17

It bridges transcription factors and RNA polymerase II, aiding transcription initiation.

Question 18

What is the role of the consensus sequence in transcription?

Answer 18

It represents common DNA sequences bound by transcription factors and RNA polymerase.

Question 19

What is a reporter gene, and how is it used?

Answer 19

A gene (e.g., GFP) linked to a regulatory sequence to monitor gene expression visually.