Lecture 11 Flashcards
What is the central dogma of molecular biology?
DNA (knows all information, no ‘doing’) –> <– RNA (messenger, interprets info from DNA, transcription and reverse transcription) –> protein (performs action, translation)
What is the definition of a gene?
A defined region of DNA that produces a type of RNA molecule that has some function.
What is the definition of transcription? What is the enzyme that is used?
Transcription is DNA dependant RNA synthesis. This is catalysed by the enzyme RNA polymerase. mRNA is catalysed by RNA polymerase II.
What are the 2 DNA strands? Which DNA strand is transcribed and why?
The 5’ –> 3’ strand is the ‘coding strand’, and the 3’ –> 5’ strand is the ‘template strand’. The template strand is used for mRNA, as it will transcribe a coding strand (5’ –> 3’) so that is usable.
How does RNA initiation work?
Begins in promoter region at TATA box (as weaker w/2 H bonds instead of 3) –> helicase enzyme helps RNA polymerase II to pull DNA strands apart –> RNA polymerase II starts transcribing along the template strand
What is RNA polymerase II primase activity?
Creates a dinucleotide by joining 2 nucleotides.
How does RNA elongation work?
RNA pol ii continues to unwind DNA, adding nucleotides and extending the RNA in a 5’ > 3’ direction. This creates tension –> the enzyme topoisomerase ii releases the tension by cutting the 2 DNA strands, making them unwind, and then sticks them together –> as RNA pol ii goes along, the parental strands wind back together and the RNA ‘floats off’
What is the function of a coding sequence?
To be the portion of DNA which is translated and turned into protein.
What is the function of the promoter region of a gene?
To be the part of the gene recognised by RNA pol ii to initiate transcription.
What is the function of the 5’ G-cap?
- prevents mRNA degradation
- promotes intron excision
- provides a binding site for the small ribosomal subunit
What is the function of the poly-A-tail?
- prevents mRNA degradation
- facilitates export of mRNA from nucleus to cytoplasm by being a signal
What are extrons and introns?
intron = intervening sequence
exon = expressed sequences, when joined together will be translated into protein, is interrupted by introns
Why can pre-RNA not translate into proteins?
Because it has introns.
What is splicing?
The removal of introns to form mature RNA, which can be translated into protein.
Where is the cellular location of transcription + translation in prokaryotic vs eukaryotic cells?
Prokaryote = both in cytoplasm
Eurkaryote = transcription in nucleus, translation in cytoplasm
