Transcription Flashcards
What happens during transcription?
A gene is copied into an RNA nucleotide sequence.
In transcription a small portion of ___ is opened and unwound to ______ the bases on each DNA strand. One of the two strands acts as a _________ for the synthesis of ___.
In transcription a small portion of **DNA **is opened and unwound to **expose **the bases on each DNA strand. One of the two strands acts as a template for the synthesis of RNA.
What are the enzymes that carry out transcription?
DNA polymerases
What do the majority of genes in a cell’s DNA code for?
Proteins
What are RNA molecules copies from coding genes called?
messenger RNA (mRNA) molecules
What are the types of RNA polymerases in eukaryotes?
RNA polymerase I, II, and III
Which polymerases transcribe genes encoding tRNA and rRNA?
Polymerase I and III
What does polymerase II transcribe?
Most genes (all that include proteins)
Eukaryotic RNA polymerases require many additional proteins, collectively called the ________ _________ _________.
Eukaryotic RNA polymerases require many additional proteins, collectively called the general transcription factors.
What do general transcription factors do?
They help to:
- **Position **RNA polymerase correctly at the promoter
- Aid in pulling apart the two strands of DNA to allow transcription to begin
- Release RNA polymerase from the promoter into the elongation mode once transcription has begun
How much of the human genome is occupied by protein-coding genes?
3%
What base is **thymine **replaced with?
Uracil
Define TATA box
A DNA sequence that indicates where a genetic sequence can be read and decoded.
The assembly of the transcription initiation complex begins when *what *binds to the TATA box?
TFIID
Where is the TATA box located?
25-35 nucleotides upstream of the transcription start site
What happens after TFIID binds to the TATA box?
The binding causes distortion in the DNA, other factors then assemble to form a complete transcription initiation complex
What makes up the transcription initiation complex?
- TFIID
- TFIIB
- RNA polymerase II
- other factors
- TFIIE
- TFIIH
What does TFIID do?
It contains DNA helicase and hydrolyses ATP to unwind the double helix
What upstream regulatory elements are there?
- GC box
- CAAT box
As well as upstream regulatory elements, what other control elements are there?
Enhancers and silencers
What elements are needed to activate transcription in a eukaryotic cell?
- Activators
- Repressors
- Coactivators
- Basal factors (positions polymerase)
What modifications are made after transcription?
- RNA splicing
- 5’ capping (7-methyl guanosine)
- 3’ polyadenylation
How is mRNA capped?
- gamma phosphate lost
- GMP added
- methylation of nitrogen arom 7 of guanosine and of carbon 2’ of ribose
What are the coding sequences of DNA called?
Exons
What are non-coding pieces of DNA called?
Introns
At what point is RNA termed mRNA?
After splicing out introns
What carries out RNA splicing?
The spliceosome
What forms the core of the spliceosome?
**snRNA(small nuclear RNA). **The rest is made from protein and RNA
Define isoform
any of several different forms of the same protein
