L9 - Gene to Protein Flashcards
What are the main steps of gene expression
Transcription of RNA from DNA
Processing of the pre-mRNA transcript
Translation of the mRNA transcript to form a protein
What are the steps of transcription
Initiation - polymerase binds to promoter
Elongation - moves downstream through the gene, transcribing DNA
Termination - detaches after terminator reached
Is RNA more or less stable than DNA? Why?
RNA is less stable as it is single stranded while DNA is double stranded
What direction is the DNA template strand
3’ to 5’ direction
What direction is the DNA coding strand
5’ to 3’ direction
What is a TATA box
A TATA box is a DNA sequence in the promoter region that indicates the point at which a genetic sequence can be read
What is the TATA box binding protein (TBP)
A transcription factor that binds to the TATA box so that RNA Polymerase II can bind
What is the main enzyme involved in synthesis of RNA during transcription
RNA Polymerase II
How many nucleotides are exposed at a time when DNA unwinds
10-20 Nucleotides
Describe elongation
Complementary RNA nucleotides are added to 3’ end of growing transcript
Double helix reforms as transcript leaves the template strand
What bonds form between RNA nucelotides
Phosphodiester bonds
Describe termination of transcription
After transcription of the polyadenylation signal, nuclear enzymes release the pre-mRNA
RNA polymerase then dissociates from the DNA
What direction is the completed RNA transcript
5’ to 3’ direction (Basically RNA version of DNA coding strand)
What are the 3 steps in mRNA processing
Capping, tailing and splicing
What is capping
A modified guanine nucleotide is added to the 5’ end of RNA transcript
What is tailing
50-250 adenine nucleotides (polyA) are added to the 3’ end
Why is capping and tailing necessary
Facilitate export, confer stability and facilitate ribosome binding in cytoplasm
What is splicing
Where introns are removed from the transcript
Where does splicing occur
At the spliceosome, within the nucleus
What is alternative splicing
A process by which different combinations of exons are joined together
Results in multiple forms of mRNA from the same pre-mRNA
How many genes in the human genome
~20,000 genes
What bonds form between amino acids to form a polypeptide chain
Peptide bonds
What is the initiator tRNA
tRNA carrying methionine (Met)
What are the 3 sites binding sites of the ribosome
A site, P site, E site
