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Lecture 8

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Department
Biology
Course
Biology 1001A
Professor
Nicholas Hudson
Semester
Fall

Description
9/18/2013 6:41:00 PM Lecture 8: Origins of Variation Independent Study Outcomes In multiple choice format, identify the . . . 1. mechanism of proofreading and likely result of proofreading defects 2. mechanism of mismatch repair 3. differences among insertion sequences, transposons and retrotransposons 4. implications of insertion of mobile elements into DNA 5. why transposons are not actually "jumping" genes 6. basic structure of retrovirus genome Make these lists: Mechanisms that Promote Inheritance of Sameness - Mechanisms that correct replication errors Mechanisms that Promote Inheritance of Difference - Mobile elements Lecture Outcomes different types of genomic variation among humans •Venter individual genome sequence showed 1.2 million variants •¼ of variant bases are SNPs (single nucleotide polymorphism) ¾ are CNV, inversions etc (includes deletions and insertions) •Each person has about 1000 CNV affecting 35% of genes Each person has about 300 variants in insertion of retro elements (eg. LINES, SINES) - Long INterspersed Elements [9]are a group of genetic elements that are found in large numbers in eukaryotic genomes. - code for the enzyme reverse transcriptase, and many LINEs also code for an endonuclease [9] [17] Short INterspersed Elements are short DNA sequences (<500 bases ) - The most common SINEs in primates are calledAlu sequences. Alu elements are approximately 350 base pairs long, do not contain any coding sequences, and can be recognized by the restriction enzyme AluI (hence the name). With about 1,500,000 copies, SINEs make up about 11% of the human genome. [13]While historically viewed as "junk DNA", recent research suggests that in some rare cases both LINEs and SINEs were incorporated into novel genes, so as to evolve new functionality.18] structure of IS elements, transposons, retrotransposons and retroviruses - IS elements only codes for transposase; transposable elements that contain only genes for transposition - Transopon: bacterial transposable element with an inverted repeat sequence at each end enclosing a central region with one or more genes (carry genes for ANTIBIOTIC RESISTENCE) - Retrotransposon: a transposable element that transposes via an intermediate RNA copy of the transposable element; makes RNA copy via transcription, then that RNA copy becomes DNA copy by reverse transcriptase, then DNA copy inserted into target site - Retrovirus: virus with an RNA genome that replicates via an RNA intermediate - Inverted repeat: enables transposase enzyme to identify the ends of the transposable element when it catalyzes transposition types of evidence that would be useful in determining how long the human genome has been infected by a given mobile element. To det how long human genome has been infected by given mobile element, you can check the mobile element’s FREQUENCY (if there are many of same mobile elements in our bodies) OR you can check if other species related to humans have the same mobile elements (if so, then the elements must have been around for a long time!) mechanism by which tautomeric shifts in DNA bases leads to alternative base pairing - Tautomerism: ability of molecule to exist in more than one form - In organic chemistry, keto-enoltautomerism refers to achemical equilibrium between aketo form (a ketone or analdehyde) and an enol (analcohol). The enol and keto forms are said to be tautomers of each other. The interconversion of the two forms involves the movement of a proton and the shifting of bonding electrons; hence, the isomerism qualifies as tautomerism. G normally pairs with C A normally pairs with T Purines: A and G Pyrimidines: C and T BUT G and T (purine + pyri
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