Transcription 101: The Big Picture
State the overall purpose of transcription within the central dogma of molecular biology.
To synthesize mRNA that carries genetic information from DNA to ribosomes for Protein production.
Which DNA strand provides the sequence that RNA Polymerase II makes a complementary RNA strand to?
Template Strand (Noncoding Strand)
What stage of transcription does RNA Polymerase bind to DNA?
Initiation
What do you call the DNA region that dictates where transcription should begin?
Promoter
Name the enzyme responsible for synthesizing mRNA in eukaryotes.
RNA Polymerase II
What are the three main stages of transcription, in order?
Initiation, elongation, and termination
Which DNA strand has nearly the same nucleotide sequence as the mRNA produced during transcription?
Coding Strand (Nontemplate)
What happens to the DNA strand when transcription begins?
The double helix unwinds and forms a transcription bubble that exposes the template strand for RNA synthesis.
What is the purpose/importance of the TATA box in transcription initiation?
This is the binding site for the TBP (TATA Binding Protein) and helps correctly position RNA Polymerase before the TSS (Transcription Start Site).
Why can transcription factors function as both activators and repressors.
Transcription factors bind to promoter and enhancer regions to initiate or prevent transcription and ensure genes are expressed only when needed.
In which part of the cell does transcription occur in eukaryotes and in prokaryotes?
In eukaryotes, in the nucleus; in prokaryotes, in the cytoplasm
In what direction is RNA built and what direction is the template strand read?
RNA Polymerase adds nucleotides to the 3’ end of the newly synthesized RNA, building 5’ to 3’ while reading off the template strand from 3’ to 5’.
During elongation, how does RNA Polymerase synthesize the RNA strand?
It moves along the template strand, adding complementary RNA nucleotides in the 5’ to 3’ direction
What is a promoter motif and what is its function?
A specific DNA sequence within the promoter that serves as a binding site for transcription factors
What is the function of the TATA-binding protein (TBP) during transcription initiation?
It binds directly to the TATA box, allowing RNA Polymerase to attach to the promoter region
What enzyme and group of proteins are required to begin transcription of a gene?
RNA Polymerase and transcription factors
If a template strand reads 5' ATG CCT TGA 3', what would be the corresponding mRNA sequence?
5' UCA AGG CAU 3'
What event causes RNA Polymerase to stop transcription and release the RNA strand?
When RNA Polymerase II reaches the termination sequence (polyadenylation signal), it detaches from the DNA template strand
What is the role of the Rho factor in transcription termination?
It binds to the RNA transcript and uses ATP energy to separate the RNA from the DNA template, ending transcription
How does the Rho factor’s structure enable its function in transcription?
Its six identical subunits form a ring that binds RNA and uses ATP hydrolysis to move along it, separating the RNA from DNA
Why is transcription necessary for protein synthesis?
DNA cannot leave the nucleus, so transcription produces mRNA to carry the genetic code to ribosomes for translation
What is one key difference between the DNA coding strand and the mRNA sequence it represents?
The mRNA contains uracil (U) instead of thymine (T)
What is the role of the Rho factor in transcription termination?
It binds to the RNA transcript and uses ATP energy to separate the RNA from the DNA template, ending transcription
Explain what has to happen to assemble the transcription initiation complex.
1. Transcription factors bind to the promoter and TATA Box
2. TBP attaches to the TATA box, allowing RNA Polymerase to bind to the promoter, which lets DNA unwind.
How do transcription factors contribute to the regulation of gene expression beyond simply initiating transcription?
They can recruit or block RNA Polymerase and other proteins at the promoter, altering the rate of transcription and ensuring genes are activated or silenced under specific conditions