HO-15 - BIO 320 - lecture 15 Reading: Ch. 8.2, 8.4, 8.5...

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5' +1 -10 -35 polymerase sigma 5' 3' 3' 3' template strand (antisense) "sense" strand start site TTGACA TATAAT CTCGTCA -35 -10 +1 AACTGT ATATTA GAGCAGT CUCGUCA RNA polymerase Incoming ribonucleotide pairs with this base RNA 5' Promoter BIO 320 - lecture 15 Reading: Ch. 8.2, 8.4, 8.5 Question bank A Text problems: Ch 8 # 17-20 Transcription AND RNA PROCESSING • In RNA, the base uracil (U) replaces thymine (T). 2' as well as 3' carbons carry an hydroxyl (OH) group. • RNA is structurally more flexible . It is usually found as a single strand , not a double helix. Depending on its sequence, a single RNA strand may fold back and base-pair with itself to form loop and hairpin structures. Some RNAs, like proteins, can have catalytic activity and make up part or all of an enzyme - a ribozyme . • 2 roles for RNA: I. Information carrier: Messenger RNA ( mRNA ) is the information-carrying intermediate between DNA and protein. Rapidly broken down and recycled after use; it makes up about 2-5% of the total RNA in a cell. Viral genomic RNA : some viruses have RNA instead of DNA as their genetic material. Transcription : Synthesis of RNA on a DNA template by RNA polymerase. Like DNA synthesis: 5' to 3' strand elongation ; new nucleotides added only at free 3' -OH group. Template DNA strand and new RNA strand are complementary and antiparallel Unlike DNA synthesis: No primer is needed : RNA polymerase can initiate transcription. Not all DNA is transcribed. Regions to be transcribed are specified by regulatory elements . Prokaryotic transcription: starting and stopping
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HO-15 - BIO 320 - lecture 15 Reading: Ch. 8.2, 8.4, 8.5...

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