Session 2: Transcription Flashcards
What is the process by which information encoded in a DNA sequence is translated into a product that has some effect on a cell/organism?
The process is known as gene expression.
What is a gene?
A gene is the basic unit of heredity, consisting of a sequence of nucleotides in DNA that encode the synthesis of a gene product, either protein or RNA.
What segments do most eukaryotic genes contain?
Most eukaryotic genes contain segments of coding sequences known as exons interrupted by non-coding sequences called introns.
What is the process called that removes introns after transcription?
The process is called splicing.
What is the antisense strand of DNA?
The antisense strand is the noncoding DNA strand, which is complementary to mRNA and serves as the template for RNA synthesis.
What is the sense strand of DNA?
The sense strand is the coding strand of DNA that is read to make mRNA during transcription.
What is a promoter?
A promoter is a specific region of a gene where RNA polymerase can bind and begin transcription.
What directs prokaryotic RNA polymerase to the promoter site?
The σ-site on the prokaryotic RNA polymerase directs the polymerase to the promoter site by binding specifically to the -10 and -35 sequences.
What characterizes prokaryotic promoter sequences?
Prokaryotic promoter sequences are characterized by two sets of sequences located 10 and 35 base pairs upstream of the transcription start site called the -10 and -35 elements.
What is a termination signal?
A termination signal is reached by RNA polymerase when it comes to the end of a sequence during transcription, terminating the transcription process.
What is the most common type of termination signal in prokaryotic transcription?
The most common type is a symmetrical inverted repeat of GC-rich sequences followed by seven A-residues that form a stable stem-loop structure in RNA.
What type of RNA makes up most of the RNA in a cell?
Most of the RNA in a cell is ribosomal RNA (rRNA), comprising about 80%.
What percentage of RNA in a cell does mRNA comprise?
mRNA comprises 3-5% of RNA in a cell.
What are the three promoter elements in prokaryotic transcription?
1) -10 2) -35 3) Upstream elements
Is transcription and translation simultaneous in prokaryotes?
Yes.
What is the nature of mRNA in prokaryotes?
mRNA in prokaryotes is polycistronic.
How many types of RNA polymerase are there in eukaryotic transcription?
There are three types of RNA polymerase in eukaryotic transcription.
Is an initiation complex formed in prokaryotic or eukaryotic transcription of mRNA?
An initiation complex is formed only in eukaryotic transcription.
What genes does RNA polymerase II transcribe?
RNA polymerase II transcribes all protein-coding genes, snoRNA genes, miRNA genes, siRNA genes, IncRNA genes, and snRNA genes.
What genes does RNA polymerase I transcribe?
RNA polymerase I transcribes 5.8S, 18S, and 28S rRNA genes.
What genes does RNA polymerase III transcribe?
RNA polymerase III transcribes tRNA genes, 5S rRNA genes, some snRNA genes, and genes for other small RNAs.
What are the steps in the initiation of transcription in eukaryotes?
- TFIID recognizes the TATA box.
- RNA polymerase II binds to the DNA promoter.
- TFIIH contains DNA helicase.
- TFIIH phosphorylates RNA polymerase II, detaching it from TFs.
What are some regulatory proteins involved in the initiation of transcription in eukaryotes?
Mediator coordinates assembly of proteins at promoter sites, and transcription activator proteins bind enhancer sequences to attract RNA polymerase II.
What is the role of RNA polymerase I?
RNA polymerase I is devoted to the transcription of ribosomal RNA genes.
