BIOL-L211 Lecture 15 Outline of Last Lecture I. Double Stranded BreaksII. Repair Mechanisms for DSBsIII. Article Outline of Current Lecture I. ArticleII. RNAIII. TranscriptionCurrent LectureRNA: Introduction to TranscriptionI. Article: "XNA: Synthetic DNA That Can Evolve" – Popular Mechanics, April 2012A. Researchers developed nucleotides capable of using synthetic compounds instead of typical sugars (forming "XNA" or xeno nucleic acid)B. Synthetic nucleic acid was different from ribose/deoxyriboseC. Suggests potential for synthetic life formsD. Currently no direct way to replicate directly (still room for development)II. RNAA. Structure1. Similar to DNA in that phosphodiester bonds link its nucleotidesa. 3' –OH connects to a 5' phosphateThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.2. Generally single stranded3. Sugar: ribose (has a 2' –OH group lacking in deoxyribose)4. Has secondary structurea. Stem-loop structure (hairpin): short stretches of complementary sequences that can base pair with each otherb. Internal loops: Unpaired nucleotides between stretches of paired nucleotides (that exist on both sides of the parallel sections)c. Bulge: Unpaired nucleotide only on one side of the parallel sections of RNAd. Junctions: site with multiple branches stemming off (with their own internal loops)B. Types of RNA (there are more than discussed in lecture, but not important) 1. rRNA: Ribosomal RNA, which is important in translation as it forms the ribosome, which recognizes the mRNA transcript and makes the proteins2. tRNA: Transfer RNA, which is also important for translation; activates amino acids and reads mRNA transcript3. mRNA: Messenger RNA, which is responsible for taking DNA information to ribosome II. TranscriptionA. RNA Polymerase (RNAP)1. No primer necessary (different than DNA polymerase), which means no primer:template junction2. Only uses one strand of DNA as a template3. Like DNA synthesis, RNA is synthesized 5' to 3'4. RNA polymerase catalyzes RNA synthesis5. Unwinds and reanneals DNA (as transcription progresses)6. Has a proofreading mechanismB. Overview1. DNA is unzipped and re-zipped as transcription proceeds2. One gene can yield multiple transcripts3. DNA Replication copies genome once per cell division4. Transcription is selective and chooses specific sections of the genome, with the potential to make thousands of copiesC. Process1. Initiationa. Promoter: DNA sequence that recruits and binds RNA polymeraseb. Transcription bubble: opening up of DNA by RNA polymerasec. +1: stands for the transcriptional start site (next lecture)d. Downstream DNA: DNA after +1 (labeled with positive numbers)e. Upstream DNA: DNA before +1 (labeled with negative numbers)2. Elongationa. RNA polymerase does its job (unwinding, synthesizing, and reannealingDNA)3. Terminationa. RNA polymerase finishes and releases mRNAb. Departs DNA
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