Transcription Flashcards
What is the flow of the Central Dogma of Molecular Biology
It is a theory that states that genetic information only flows in one direction: DNA makes RNA, RNA makes proteins. Or, RNA directly to proteins
What are the macromolecules involved in the Central Dogma of Biology and their roles
DNA - Storage of genetic information
RNA - Messenger of genetic information
Proteins - Workers/implementers of genetic information
What is transcription and translation
Transcription is the transcribing to the template strand of DNA to synthesis a complimentary strand of messenger RNA
Translation is the translation of the messenger RNA into a protein via polypeptide chain synthesis at a ribosome
What is gene expression
The process by which information from a gene is used in the synthesis of a functional gene product (a protein or non coding RNA)
What is non coding RNA
An RNA molecule that will not give rise to a protein and has some other function
What is a gene
A defined region (sequence) of DNA that produces a type of RNA molecule that has some function
May contain sequences responsible for regulation of the syntheses of RNA, sequences that produce RNA, and sequences responsible for the further processing of RNA
What enzyme catalyses transcription, and what does it do
RNA polymerase
RNA polymerase synthesis mRNA by catalysing formation of phosphodiester bonds between ribonucleotides
It selects the correct nucleotides to incorporate based on the sequence of the DNA which is being transcribed
What are the two DNA strands, and which is transcribed
DNA has two complimentary strands
The coding strand (5’ to 3’), and the template strand (3’ to 5’)
RNA polymerase transcribes the template strand to produce a strand of mRNA complimentary to the template strand, and Identical to the coding strand
What are the 3 stages of transcription
Initiation
Elongation
Termination
Outline the initiation step
Transcription factors bind to the TATA rich region, and other regions of the promoter
RNA polymerase 2 binds, forming a transcriptional initiation complex with the transcription factors
The two DNA strands seperate and RNA polymerase 2 starts mRNA synthesis without the need of a primer
Why can RNA polymerase 2 being transcription without a promoter
RNA polymerase 2 has an internal 3’ hydroxyl group allowing it to being translation on its own
What releases tension in the DNA strand caused RNA unzipping it
Topoisomerase
Outline the elongation step
RNA polymerase 2 uses the template strand, which runs 3’ to 5’, as a template and inserts complimentary RNA nucleotides in the 5’ to 3’ direction. mRNA synthesis is anti parallel to the template strand
Which part of the gene is transcribed from DNA into mRNA
The 5’ UTR, the Coding Sequence, and the 3’ UTR
Which parts of the gene are translated from mRNA to protein
The coding sequence
What is the function of a promoter region
It is a DNA segment that is recognised by RNA polymerase to initiate transcription
What region of the promoter region is particularly important and why
The TATA rich region
AT (adenine bond thymine) are bound by two hydrogen bonds, compared to the 3 hydrogen bonds of GC (guanine bond cytosine). Hence a AT bond rich region will be easier to seperate than one that is not. This allows RNA polymerase to easily seperate the coding and template DNA strands, to then subsequently begin transcription
What are the main functions of UTRs
Regulatory elements that influence gene expression at the transcriptional or translational level.
5’ UTR facilitates the addition of a 5’ G Cap
3’ UTR facilitates the addition of the Poly A Tail
What is the function of the 5’ G cap
It prevents mRNA degradation, promotes intron excision, and provides a binding site for the small ribosomal sub unit
What is the function of the Poly A Tail
It prevents mRNA degradation and facilitates the export of mRNA from the nucleus to the cytoplasm
Why are mutations in the non coding regions harmful
By altering the non coding region, a variant in non coding DNA can turn on a gene and cause a protein to be produced in the wrong place or at the wrong time. Alternatively, it could reduce or eliminate the production of the desired protein when and where it is needed
What are eukaryotes, prokaryotes, and where does transcription and translation occur in them respectively
Eukaryotes are a domain of organism whose cells have a nucleus. Transcription occurs in the nucleus, and translation occurs in the cytoplasm. Transcription and translation are not coupled.
Prokaryotes are a domain of organism whose cells lack a nucleus, and other membrane bound organelles. Transcription and translation occur in the cytoplasm. Transcription and translation are coupled.
