TRANSCRIPTION Flashcards
PROCESS OF TRANSCRIPTION
-RNA polymerase binds itself to the promoter region of the DNA double helix
-2 strands of the structural gene uncoil from the site of the polymerase binding
-DNA helicase catalyses the unzipping of the gene as hydrogen bonds between the complementary nucleotide bases are broken
-the free RNA phosphorylated nucleotides move in and line up opposite the exposed based on the template strand according to the complementary base pairing rules
-catalysed by RNA polymerase, the nucleotides form temporary H bonds with the exposed bases in the template strand
-hydrolysis of the phosphorylated nucleotides releases the extra phosphate groups, releasing energy
-moving in the 5’ to 3’ direction, the RNA polymerase makes use of the released energy to form phosphodiester bonds that links adjacent RNA nucleotides
-RNA synthesis stops as soon as the polymerase reaches the terminator region
-the result is a completed RNA chain which detaches from the DNA
why is it important that RNA is just temporarily bonded?
proteins will not be made fast enough
why are hydrogen bonds important?
important for complementary base pairing to keep the bases in sequence so they carry out their roles
what region is upstream?
the promoter region
what region of the structural gene is downstream?
the terminator region
what is a difference in one of the phosphorylated nucleotides in RNA compared to in DNA?
UTP instead of TTP
how will the RNA sequence if bases in the new RNA strand compare against the base sequence of the coding strand?
same except the base T is swapped out for a U
what is the direction/ polarity of the template strand?
opposite to the direction of DNA synthesis so 3’ to 5’ direction
what is the name of the section of the nuclear DNA that is involved in the first stage of protein synthesis?
transcription unit
what does 5’ end attach to
phosphate group
what does 3’ end attach to
hydroxyl
Is the sequences of bases on the mRNA strand the same as the coding strand or the template strand?
the coding strand-
the coding strand is complementary to the template strand which is complementary to the mRNA sequence and so the mRNA sequence must be the same as the coding strand
Which direction does RNA polymerase work?
RNA strand is synthesised in the 5’ to 3’ direction BUT RNA polymerase reads the template DNA strand in the 3’ to 5’ direction.
What happens after the mRNA strand detaches from the DNA and why?
the double helix reforms and this is important to stop the bases from becoming mutated because the cytoplasm and nucleus are quite harsh environments so DNA zips back up again
What is formed in eukaryotes before mRNA is formed?
pre-mRNA
