CELS 191 Lecture 11 Flashcards
what is gene expression
the process by which information from a gene is used in the synthesis of a functional gene product
what is a gene product
a protein or a non-coding RNA sequence - an RNA molecule that will not give rise to a protein and has some other function
what is a gene
a defined region (sequence) or DNA that produces a type of RNA molecule that has some function
what is transcription
DNA-dependent RNA synthesis (synthesis of an ssRNA molecule, using a dsDNA molecule) is catalysed by the enzyme RNA polymerase
what enzyme is used to catalyse transcription
RNA polymerase
what is the function of RNA polymerase and what does this form
catalyses the extension of the 3’ of an RNA strand by one nucleotide at a time - it selects the correct nucleotide to incorporate into the RNA based of the sequence of DNA which is being transcribed - this forms an RNA molecule (transcript) by catalysing the formation of phosphodiester bonds between ribonucleotides
what enzyme catalyses mRNA synthesis - transcription
RNA polymerase 2
RNA polymerase 2 has a primase function what is a primase function and what does RNA polymerase create with its primase function
it can create a new strand of RNA by using its active site to bind together two ribonucleotides and catalyse the. formation of a phosphodiester bond to form a dinucleotide which then provides a 3’ end for further addition of nucleotides
which direction does the coding strand run in
5’ to 3’
which direction does the coding strand run in
3’ to 5’
which strand (coding or template) is mRNA transcribed from
the template strand to create a copy of the coding strand
what are the three stages of transcription
Initiation
elongation
termination
what is the name of the region where transcription starts from
the promoter region - the TATA box
what is the TATA box and what is its function
an area on the DNA strand where we have lots of Adenine and Thymine nucleotides. these bonds are weaker than C-G bonds because they only have 2 hydrogen bonds holding them together. because of this it is easier for the DNA to be split apart here and for transcription to start
what are the first things to bind to the TATA box and other regions of the promoter and what is their function
transcription factors recruit RNA polymerase to bind to the TATA box because it can’t bind on its own
once the RNA polymerase is bound to the TATA box of the promoter what does it create with the transcription factors
a transcriptional initiation complex
which way does transcription run
5’ to 3’ direction
what is the function of the enzyme helicase and where does it bind
is ‘unzips’ the DNA by breaking H-bonds between the DNA base components - it binds to the TATA box
which form of chromatin is transcriptionally active (less tightly packed) and which form is transcriptionally inactive
euchromatin is less tightly packed so it allows access for the transcriptional machinery and is therefore transcriptionally active whereas heterochromatin is transcriptionally inactive
which direction is the DNA strand being read by RNA polymerase and which direction is the resulting RNA strand being formed in
RNA polymerase 2 uses the template strand which runs in the 3’ to 5’ direction as a template and insert complimentary RNA nucleotides in the 5’ to 3’ direction
why is helices no longer needed after the TATA box
because the RNA polymerase 2 has weak ‘unwinding’ abilities
what is the name of the enzyme used to release the tension (supercoil) that build up ahead of the RNA polymerase 2
topoisomerase
what is the difference between transcription and translation
transcription uses DNA as a template to produce mRNA
translation uses that mRNA to produce proteins
what are UTRs and what is their function
UTRs and untranslated regions - there is one on the 5’ end and one on the 3’ end.
