Gene Expression Flashcards
What is the 3 stage process involved in making RNA and making a polypeptide?
Initiation
Elongation
Termination
What happens in initiation in transcription?
Promoter recognition
Transcription initiation factors
RNA polymerase
What happens in elongation in transcription?
5’ to 3’ chain growth
What happens in termination in transcription?
Sequence dependent
What does the transcription factor recognise on the DNA sequence?
TATA box
What happens after the TATA box has been recognised?
RNA polymerase (promoter) binds over transcription factor First building block is produced from the first bases to the left of RNA polymerase - this is where transcription starts
What is the mRNA transcript made using?
Makes complementary strand to DNA template strand
DNA coding strand not used in transcription
Which direction does transcription work in?
5’ to 3’
What is RNA processing and what does it include?
When pre-mRNA is made into mature mRNA
Capping, tailing/polyadenylation, splicing
What is capping?
Methylated guanine added to 5’ end of sequence in a 5’-5’ linkage
Provides protection and plays role in translation
What is polyadenylation?
Adding a polyA tail to 3’ end of sequence
Uses specific endonuclease to cleave site from RNA polymerase
Uses polyA polymerase to add polyA tail
What is splicing?
Introns are removed from pre-mRNA to leave coding sections which are joined together
Produces mature mRNA
What is the structure of ribosomes in prokaryotes?
3 rRNAs and 56 proteins
30S and 50S subunits
70S ribosome
What is the structure of ribosomes in eukaryotes?
4 rRNAs and 82 proteins
40S and 60S subunits
80S ribosome
Describe the features of the genetic code
Triplet code, degenerate Non-overlapping ‘Comma-less’ (no gaps) 5’ to 3’ templat read through producing N to C polypeptide chain extension Adaptor molecule needed, tRNA