CSB428H1 Lecture Notes - Lecture 1: Fruit Anatomy, Genome Size, Meiosis

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14 Aug 2016
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Lecture 3: Genome Evolution and Polymorphisms
Band at bottom is cut and pasted 2 times after being flipped = inversion
Maize experiment
oWorked on colour gene
oNormal colour 0s uniformly is purple
oTransposon = dissociator
oInactive enzyme  may or may not bind to precursor  colourless kernels (can
convert it to purple colour)
oSaw spots = dissociator jumped out of gene + restored function of gene
Jumping early in kernel development = large purple sector, late in
development = small sector
oOuter kernel = pericarp
Transposons move on their own accord
Structures important for movement of transposons
oDirect and inverted repeats
oTransposon inserted = causes direct repeats  how to get direct repeat
If transposon is by transposase – cut so that it can be cut and put into
another place (staggered cuts)
oEnds of transposon are inverted repeats
Process of bacterial transposition  Transposase binds to inverted repeats at ends,
creates cleavage in donor DNA, captures target DNA, mixes 2 strands, repair synthesis
creates direct repeats at end
oDonor DNA cuts is non-specific
Process in eukaryotes  cut and paste, coming out of donor DNA, selects recipient DNA
and moves from one place to another
oFoot print = what is left behind  where transposon is from (identified by short
direct repeats next to each other)
Replication, transcription and reverse transcription  used by retrotransposons
oHost RNA polymerase and transcribes RNA of transposable element, transposon
located gene encodes reverse transcriptase which makes RNA copy into DNA,
DNA is converted dsDNA + replicate transposon which can work, move and stay
in same place (mutation = moved, stayed = genome size changes)  used to
create new gene families
Repetitive DNA in humans due to transposons
oMost copies are silenced by mutations (mutations in inverted repeats or
transposons)
Every time meiosis happens it occurs one or more times anywhere along the
chromosomes
FOXP2 encodes a transcription factor (tells genes when to be expressed or silenced)
oWhy apes don’t have same complex language
DNA #2 has an restriction fragment length that is different – do gel analysis to see this
(PICTURE)
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