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BIL 250 Study Guide - Midterm Guide: Transposase, Cointegration, Restriction Enzyme

Course Code
BIL 250
Kevin Mc Cracken
Study Guide

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Transposable Elements: cause changes to genes
Encode proteins (prokaryotes & eukaryotes)
Cut & Paste- move DNA directly into new position
Copy & Paste- replicates DNA and integrates somewhere else
Retrotransposons (eukaryotes) (48%)
Encode RT and make DNA copies of RNA, new DNA integrates
In Bacteria/Prokaryotes
Insertion Sequences (IS): simplest tp element
Contains only genes needed to mobilize & insert
Size: 768 bp-5kb
I“1: i E. Coli’s glatose opero, ith 4-19 copies in E. Coli
Ends = Inverted Terminal Repeats (ITRs)
Disrupt coding or regulatory regions
Alter expression
Cause deletions & inversions in adjacent DNA
1. OG copy in place, new copy inserts randomly
2. Transposase (enzyme coded by IS) required for transposition
3. Otherwise IS would use host enzyme
4. Initiates: transposase recognizes ITRs
5. Site of integration = target site
6. Staggered cuts made in DNA at target site by transposase
IS elements insert
DNA Poly and Ligase fill gap
Transposase = restriction enzyme
7. Small direct repeats (same orientation) = target site duplications
Transposons (Tn): more complex element
Composite Transposons: carry genes flanked by IS elements
How: IS elements supply transposase and ITR recognition signals
Tn10-contains tetracycline resistance gene, conservative transposition
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