Flashcards in Chapter 10 Questions Deck (25)
Why is RNA degraded under alkaline conditions?
Because it has a free hydroxyl group on the 2' carbon atom. This makes it very nucleophilic and more likely to react.
Can RNA form a secondary structure?
Yes. Even though it is usually single stranded, short complementary regions within a nucleotide strand can pair and form secondary structures.
What does the mRNA molecule do after attaching to the ribosome?
It specifies the sequence of the amino acids in a polypeptide chain and provides a template for the joining of those amino acids.
What functions do lncRNA's provide?
A variety of functions, including regulation of gene expression.
What is the purpose of shortened transcription for the cell?
Because not all genes are needed at the same time, or in the same cell, constant transcription of all the cell's genes would be highly inefficient.
Where is the promoter located in most transcription units?
Next to the transcription start site, but it is not transcribed itself.
When does transcription stop?
After the terminator has been copied into RNA.
How is the sequence of the non template strand written?
With the 5' end on the left and the 3' end on the right.
What is the direction of transcription?
5' to 3'
How is the action of RNA polymerase enhanced?
By a number of accessory proteins that join and leave the polymerase at different stages of the process.
What does transcription initiation require?
That the transcription apparatus recognizes and binds to the promoter.
Why is promoter binding important?
It determines the frequency of transcription for a particular gene.
What is embedded in the nucleotide sequence of the promoter?
Information for where the transcription apparatus will start transcribing, which strand is to be read, and in what direction RNA polymerase will move.
What do consensus sequences determine?
Which strand will the template strand for transcription and the direction of transcription.
How do rho independant terminators terminate transcription?
With inverted repeats, and a series of 8-0 A's that follow the inverted repeat. The series of A's create a string of U's on the RNA stand, which causes the RNA polymerase to pause and allows a hairpin structure to form. The hairpin structure destabilizes the DNA-RNA pairing.
How do rho dependant terminators terminate transcription?
They have a stretch of unstructured RNA called the rut site that serves as a binding site for the rho protein. When RNA polymerase reaches the terminator, it pauses so that the rho protein can catch up, and the rho protein uses helicase activity to unwind the DNA-RNA hybrid.
What does the concept of co linearity suggest?
The number of nucleotides in a gene should be proportional to the number of amino acids in the protein encoded by that gene. However, eukaryotic cells were found to have far more DNA than is required to encode proteins (it loops out from hybridized molecules), causing this to seem inaccurate.
What is the purpose of separating transcription and translation in eukaryotes?
It allows for eukaryotic RNA to be modified before it is translated.
What is the purpose of a 5' cap?
It increases the stability of mRNA and influences the removal of introns.
What is the purpose of the polyatail?
Increases the time in which it remains intact and available for translation before it is degraded by cellular enzymes. Also provides stability and plays a role in the export of mRNA to the cytoplasm.
How is rRNA processed after transcription?
A precursor RNA molecule is methylated in several places, then cleaved and trimmed to produce the mature rRNA's that make up the ribosome.
How is tRNA processed after transcription?
It trimmed by having nucleotide's removed from the 3' and 5' ends and some base-modifying enzymes change the standard bases.
How can double stranded RNA molecules form?
By transcription of inverted repeats into an RNA molecule that then base pairs with itself; by simultaneous transcription of 2 different RNA molecules that are complementary to one another and pair; or by infection by viruses.
What do siRNA and miRNA inhibit?
siRNA inhibits transcription and miRNA inhibits translation.