Lecture 9: CSF Gene to Protein Flashcards
What is genotype?
An organism’s hereditary information
What is phenotype?
Actual observable or physiological traits
What is gene expression?
The process of forming a functional product from DNA
DNA -> RNA -> Protein
What are the 3 steps to gene expression?
Transcription
Processing
Translation
What are the 3 steps to transcription?
Initiation -> polymerase binds to promoter
Elongation -> moves downstream through the gene, transcribing RNA
Termination -> detaches after terminator reached
What is the difference in bases in mRNA and DNA?
Uracil takes place of thymine in mRNA
What is the significance of uracil replacing thymine in mRNA?
Thymine is more stable -> DNA is the inherited material hence needs to be more stable
Explain how initiation process occurs during transcription
Initiation is the assembly of proteins required before transcription can commence
- DNA contains a promoter region in which the TATA box can be found
- Several transcription factors bind to the promoter region (including TATA box binding protein [TBP])
- This changes the shape of the promoter region allowing RNA polymerase II to bind along with more transcription factors to form the transcription initiation complex
What is the TATA box?
A sequence of DNA found in the promoter region which marks where transcription should be initiated
What is TBP?
TATA box binding protein is a transcription factor that binds to the TATA box of the promoter region forming transcription initiation complex.
Explain how the elongation process occurs during transcription
10 - 20 nucleotides become exposed at a time as DNA unwinds
Complementary RNA nucleotides are added to the 3 to 5 DNA sequence (template strand).
As complementary base pairs form between mRNA and DNA, the 3’ end forms a phosphodiester bond with the 5’ end of incoming nucleotide.
Double helix reforms as transcript leaves the template strand
Explain how the termination process occurs for transcription
After transcription of the polyadenylation signal, nuclear enzymes release the pre-mRNA and RNA polymerase then dissociates from the DNA
What is the polyadenylation signal?
A sequence of nucleotide bases that signal the termination of transcription hence the release of pre-mRNA and RNA polymerase
What are the 3 steps to processing stage of gene expression?
Capping, tailing, splicing
What are exons?
Coding regions of mRNA strand including untranslated regions (UTR)
What are introns?
Non-coding regions intervening exons
What is UTR?
Untranslated regions at 5’ and 3’ ends of the mRNA
What is capping?
A modified guanine nucleotide is added to the 5’ end (lid on top)