Prokaryotic Genes Flashcards
What is a gene?
Segment of DNA that encodes information for a protein or functional RNA, as a linear sequence of nucleotides.
What are the two major components of a typical gene?
- Information to make functional protein or RNA
- Information to control when it makes the protein/RNA it codes for.
Why is it important there are mechanisms to control genes?
Don’t want cellular products to be produced all the time without control;
Can turn them on/off in response to cellular events;
Adjust the amount of product made by each gene
What is the promoter element of a gene?
Regulates gene expression (when and how much a gene gets used)
Where is the promoter element located on a gene?
upstream (5’ end)
What is the protein coding sequence (CDS)?
Contains the information to make the protein.
Where is the CDS located?
Downstream from the promoter.
What initiates transcription for prokaryotes?
RNA polymerase binding to promoter.
Where does transcription begin in prokaryotic genes?
At the +1 transcription start site
Which portion of the gene gets translated to a protein in prokaryotes?
The CDS
What is the start codon in prokaryotes?
ATG/AUG
What is the stop codon (typically) in prokaryotes?
TAA, TGA, TAG
What are the 5’ and 3’ UTRs in prokaryotic genes?
The regions of mRNA which do not get translated at the 5’ and 3’ ends.
What is the difference in transcription for genes that code for proteins as opposed to genes that code for functional RNAs in prokaryotes?
RNA is made directly from transcription. The RNA may get post-transcriptionally modified but no translation occurs as protein CDS and UTRs do not exist.
What is the main function of the prokaryotic promoter?
Attract RNA polymerase
What are the three elements typically found in the prokaryotic promoter element?
UP element, -35 element, -10 element
What is the consensus -35 element in the prokaryotic promoter?
TTGACA
What is the consensus -10 element in the prokaryotic promoter?
TATAAT
What is a consensus sequence?
Sequence of a conserved genetic element representing the most frequently occurring nucleotide at each position.
What nucleotide base is usually the start site in prokaryotic transcription?
A
How do you identify the transcription start site in prokaryotic genes?
Count from the middle of the -10 element.
What does the relative position of -10 and -35 do?
Tells RNA polymerase which way to go.
In which direction does RNA polymerase move along a prokaryotic gene?
From 5’ to 3’ on the coding/non-template strand.
What is the coding strand in transcription?
The strand that the mRNA will be an exact copy of.
What is the template strand in transcription?
The strand that RNA polymerase moves along and uses as a base pairing template.
How does transcription begin?
RNA polymerase binds to -35 and -10 elements and unwinds DNA.
In which direction is the mRNA assembled?
5’ to 3’
Can genes be coded for on only one strand?
Can be coded for on either side; depends on the particular gene.
