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Midterm

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


Department
Biology
Course Code
BIL 250
Professor
Kevin Mc Cracken
Study Guide
Midterm

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CHAPTER 7B
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)
Effects:
Disrupt coding or regulatory regions
Alter expression
Cause deletions & inversions in adjacent DNA
Crossing-over
Process:
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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