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Chapter 7b

BIL 250 Chapter Notes - Chapter 7b: Transposable Element, Insertion Sequence, Transposase

Course Code
BIL 250
Kevin Mc Cracken

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Chapter 7B: Transposable elements
Plasmid- cut off from nucleus??
Transposable element: mobile genetic elements of a chromosome that can move to different
locations on the genome
Transpose to or from a cell’s chromosome, plasmid, or phage chromosome.
Transpose to or from the same or different chromosomes
Nonhomologous recombination: these transposable elements insert into DNA that has no
sequence homology with it
Genetic changes
Inserted into genes
Inserted into sequences to modify gene expression
Make Chromosomal mutations
The two types of transposable elements:
1. Encode proteins (euk and prok)
1. Move DNA to a new position
1.1. Cut and paste mechanism
2. Replicate DNA and integrate replicated DNA somewhere else
I. Copy and paste mechanism
2. Retrotransposons euk only
c. encode reverse transcriptase and makes copies of RNA
transcripts from DNA. new DNA copies integrated at different sites
c. RNA dependent polymerase
c.1. RNA→ DNA
Two examples of transposable elements in prokaryotes:
1. Insertion sequence (IS) elements
1. Simplest
2. Found in chromosomes and plasmids
3. Transposase for mobilization and insertion
4. 768 bp to 5kb
5. First identified in E.Coli
6. IS ends have inverted terminal repeats (ITRs)
7. May
1.1. Disrupt coding sequence or regulatory regions
1.2. Alter nearby genes
1.3. Cause deletions or inversions in adjacent DNA
1.4. Crossing-over
2. Transposition
1.1. OG copy remains in place while the new one is inserted
1.2. Uses enzyme transposase
1.3. Uses host enzymes for replication
1.4. Starts when transposase recognizes ITR
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