RNA & Transcription Flashcards
The degenerate code allows for what?
Multiple codons to encode for the same AA
Initiation (start) codon
AUG –> Methionine
Termination (stop) codon
UAA, UGA, UAG
Mutation that affects one of the nucleotides in a codon
Point mutation
Nonsense mutation
produces premature stop codon
aka truncation
Missense mutation
substitution of one AA for another AA
The three nucleotides of a codon are referred to as
the reading frame
Mutation where some number of nucleotides are added or deleted from the mRNA sequence
Frameshift
Enzyme that unwinds DNA double helix in transcription
Helicase & topoisomerase (prevents supercoiling)
What is the name of the strand that mRNA is synthesized from?
Anti-sense strand (template)
Enzyme responsible for synthesizing mRNA strand during transcription
RNA polymerase II
Specialized DNA regions that initiates transcription of a particular gene
Promoter region
RNA polymerase binding site in promoter region is known as
TATA box
What helps RNA polymerase locate and bind the TATA box in the promoter region of DNA?
Transcription factors
Major difference between RNA polymerase and DNA polymerase?
RNA polymerase does not require a primer to start generating a transcript like DNA polymerase does in replication
What is the relationship between the mRNA strand and the coding (sense) strand?
They are exactly identical with the exception that all T residues are replaced with U residues in mRNA
The first base transcribed from DNA to RNA is defined as
+1 base of that gene region
T/F: no nucleotide in the gene is numbered 0
True
Numbers to the left of the +1 start point (upstream, or toward 5’ of coding strand) are +/-?
negative
Numbers to the right of the +1 start point (downstream, or toward the 3’ end of coding strand) are +/-?
positive
Upstream refers to what end of both the coding/template strands?
5’
Downstream refers to what end of both the coding/template strands?
3’
How many bases upstream from the first transcribed base is the TATA box?
25 bp located at (-25)
Posttranscriptional modifications include:
5’ cap (7-methylguanylate triphosphate)
3’ poly-A tail (polyadenosyl)
Splicing is accomplished by the splicesome which contains what two molecules?
SnRNA (small nuclear RNA) and snRNPs (small nuclear ribocucleoproteins)
Lariat
name given to the excised noncoding regions of hnRNA
What function does the 5’ cap serve?
Recognized by the ribosome as the binding site and protects from degradation
What function does the poly-A tail serve?
Protects mRNA from the instant degradation it encounters as soon as it exits the nucleus … the longer the poly-A tail the more time the mRNA will survive before it is digested by the cytoplasm
