Transcription Flashcards
(24 cards)
What are the two steps of gene expression? briefly explain them
Transcription: DNA sequence copied into mRNA
and translation: Ribosomes read mRNA code and assemble amino acids into a polypeptide
What is the language difference for transcription and translation?
DNA -> mrna is in same language of nucleotides, mrna -> protein is in a different language
One sentence to describe transcription
The synthesis of mRNA using a DNA template
In a nutshell describe transcription
Catalyzed by the RNA polymerase enzyme, nucleotides added to 3 end of MRNA, mRNA grows in the 5 to 3 direction which synthesizes a strand
Template strand def
DNA strand complementary to the newly made RNA
coding strand def
the strand thats not the template strand
Will the newly made RNA have the same sequence as the template strand or the coding strand
Same as coding except uracil replaces thymine
What does RNA polymerase do?
enzyme that synthesizes RNA from DNA, catalyzes phosphodiester bond formation, synthesizes from 5 to 3 (reading from 3 to 5)
Does RNA polymerase have helicase activity?
Yes
3 steps of transcription
Initiation, elongation, termination
What happens during initiation step of transcription?
RNApol and transcription factors(proteins that help recruit RNA pol) bind to the promoter
What is a promoter? where is it found
region of DNA that includes start point and TATA box, found on coding strand
What happens during elongation of transcription?
RNA pol synthesizes mRNA from 5 to 3
Does transcription require a primer?
No, RNA pol can start synthesis directly on the DNA template
How does termination in transcription work for prokaryotes
RNA pol transcribes a terminator sequences causing it to detach from mRNA, and mRNA is released and ready
How does termination in transcription work for eukaryotes
Termination sequence reaches, and mRNA is released as pre mRNA must be processed
How must pre mrna be further processed?
addition of 5 cap, poly A tail, splicing
why is mRNA processing important
transport, stability, recognition
What is a 5 prime cap and what does it do?
It is a modified guanine nucleotide that is added to the 5 prime end of mRNA,
- protects degradation
- attachment of ribosomes
- facilitate transport out of nucleus
What is a poly A tail and what does it do
50-200 adenine nucleotides added to 3 prime end of mRNA,
- protects against degradation
- attachment of ribosomes
- facilitates transport out of nucleus
What is RNA splicing and what does it do? What are introns and exons
Introns: non coding sequences, Exons: coding sequences
Introns are removed from the pre RNA
What does the final mRNA structure ready for translation look like?
5 cap, leader sequence(5 UTR), Coding sequences, trailer(3UTR), poly A tail
True or False? Both strands of DNA can be a coding or template strand, because RNApol reads DNA from 3 to 5 on both strands
True
What are the stop codons?
UAA, UAG, UGA
