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Lecture 3

BIOB11H3 Lecture Notes - Lecture 3: Transposase, Transposable Element

Biological Sciences
Course Code
Dan Riggs

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Lecture 3 Genome Evolution, Gene Mapping and
- Karyotype: Determined by x-some bonding
- Mobile Genetic Elements: Transposons
Transposition: Transposon/transposable element
- Barbara McClintock: ‘controlling elements of maize/corn’,
Nobel prize in 1983
Individual colourless kernel if transportation occurs late in
development get small spot of pigment
If transposition occurs early: large coloured sector, due to
transposon jump early in development
You take recipient and repeat, insert transposable
elements that after
transposition you have
Generation of Direct Repeat
1. Target/recipient site
2. Staggered cuts are made
3. End structure
4. Transposon inserts
5. Repair synthesis generate
direct repeat
“Other picture is cut/paste
method of bacterial
Little DNA that donates
DNA, transposase binding,
then cleavage to target DNA,
integration occurs and a results in strip with donor-DNA-transposon
DNA-donor DNA
It’s non replicative, replicative involves RNA intermediates called retrotransposons
Genetic and Molecular Mapping of Genes
- Genetics Approach: Examine recombination frequency b/w 2 traits, usually visible, to
estimate distance b/w 20linked genes
- Distance b/w genes on x-some proportional to probability that recombination
will occur b/w them
- Centimorgan: Map unit of recombination; 1cM=1% recombination b/w 2 linked
- 3 crossovers:
1. If genes are far apart (A and C), then any of 3 crossovers will generate
2. If genes are closer together, (A and B), recombination frequency b/w them
will be lower
3. % recombination b/w 2 genes is proportional to distance b/w them
- Molecular Approach:
Use ‘crude’ information from genetic map general ‘order’ and linkage of genes
Sequencing generates huge datasets many sort and long sequences, genomics
Computational methods comare and order gene prediction, assembly into ;contigs’,
Exact distance b/w genes can be determined
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