MCB 121 Lecture 7

MCB 121 Lecture 7 - MCB 121 - Lecture 7 Outline:...

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MCB 121 - Lecture 7 Outline: Transposons Retroviruses Immunoglobulin gene rearrangement - V (D) J recombination ------------------------------------------------------------------------------------------------------------------------- Transposition: The transfer of a chromosomal segment to a new position on the same or another chromosome Transposons : a DNA element that moves (RNA intermediate) Transposase : the enzyme that catalyzes transposition = enzymes that expressed from open reading frame in transposons, which catalyze excision and insertion of mobile elements into the genome. = enzyme that promotes nicking and ligation of transposon to go to target sequence Two types of elements: Autonomous - contains all the information contained within the transposable elements to excite and integrate to another region of genome = encode the proteins required for transposition. ex. LINEs = Long interspersed nuclear elements - moves DNA or RNA intermediate - has two ori. (open reading frame) : ORF1 and ORF2 * proteins which function to insert the LINE element into a chromosome * LINE element would be the RNA * It inserts using reverse transcriptase * reverse transcriptase: use RNA as template to synthesize DNA * thus RNA is interspersed into the new genome to where it will exist. * reverse transcriptase is also used: 1) viral infection 2) cDNA library 3) telomerase Nonautonomous - use protein enzymes from other sources (transposable elements) in order to integrate = require transposition factors encoded by other elements. ex. SINEs = short interspersed nuclear elements - contains the sequence which allows itself to target into the DNA - but use the ORF from the LINEs element to catalyze the DNA synthesis as insertion requires. - example of SINEs: Alu (elements that can be mobilized by "stress")
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Total Genome: 30% LINES/SINES 10% DNA transposons 8% Retrotransposons - includes Latent retro-viruses Purposes of transposons? - can lead to evolution of new genes. (duplication of gene can evolve to another function) - parasite of the genome, hard to get rid of them due to their numbers - diversity of immune system evolve from transposons How transposons can mess up your genome: process of recombination double strand DNA break can be repaired by homologous recombination. Homologous recombination is a type of repairing process where these sequences with double strand
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MCB 121 Lecture 7 - MCB 121 - Lecture 7 Outline:...

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