Why model organisms

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Introduction
Why model organisms ?
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What is the model plant ?

• Arabidopsis is a small annual weed belonging to
  the Brassicaceae family.
• Several species belong to the Arabidopsis genus,
  the most extensively used in research is
  Arabidopsis thaliana.

• Arabidopsis thaliana (common name thale cress or
  mouse eared cress).

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What is Arabidopsis?

• Although of no inherent economic value,
• Arabidopsis offers many advantages for rapid
• genetic and molecular analysis including
• small size,
• rapid life cycle,
• small simple genome,
• prolific seed production
• availability of numerous mutations
• This weed has thus become the focus of a genome
  project to understand the biology of a flowering
  plant at the molecular level

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Stocks held here

• NASC began in spring 1991 with only 200 stocks
• Fourteen years on, NASC currently holds around
  500,000 stocks

450,000
200,000
20,000
200
1991
1999
2002
2004
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NASC distributes

• over 30,000 tubes of seed a year
• fulfilling 4000 orders
• for over 3000 registered users.
• in 37 countries

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Why so many stocks ?
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Reverse genetics (Find the mutant by PCR
fingerprinting)
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Reverse genetics
Make it harder
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Reverse genetics
Each tube 1000 plants
Then do it again 1 tube 100 plant Then 1 tube
10 plants Then 1 tube per plant
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In silico Reverse genetics
When you have a whole DNA sequence you dont need
wet biology
gcttaggctgcgcgcgtataactgatcgatcgaaacccgggcatgcccac
gacgacacgatcgactcgctagtgcgcgtatgctgatgctagacg
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Reverse genetics
To find the mutation - search for the flanking
tag -gt tgatgctagacgg
gtataactgatcgatcgaaacccgggcatgcccacgacgacacgatcgac
tcgctagtgcgcgtatgctgatgctagacggcttaggctgcgcgcgtata
actgatcgatcgaaacccgggcatgcccacgacgacacgatcgactcgct
agtgcgcgtatgctgatgctagacggcttaggctgcgcgcgtataactga
tcgatcgaaacccgggcatgcccacgacgacacgatcgactcgctagtgc
gcgtatgctgatgctagacggcttaggctgcgcgcgtataactgatccgg
gcatgcccacgacgacacgatcgactcgctagtgcgcgtatgctgatgct
agacggcttaggctgcgcgcgatcgatcgaaacccgggcatgcccacgac
gacacgatcgactcgctagtgctgatgctagacggcttaggctgcgcgcg
tataactgatcgatcgaaacccgggcatgcccacgacgacacgatcgact
cgctagtgcgcgtatgctgatgctagacggcttaggctgctataactgat
cgatccacgatcgactcgctagtgcgcgtatgctgatgctagacggctta
ggctgcgcgcgtataactgatcgatcgaaacccgggcatgcccacgacga
cacgatcgactcgctagtgcgcgtatgctgatgctagacggcttaggctg
cgcgcgtataactgatcgatcgaaacccgggcatgcccacgacgacacga
tcgactcgctagtgcgcgtatgctgatgctagacggcttaggctgcgcgc
gtataactgatcgatcgaaacccgggcatgcccacgacgacacgatcgac
tcgctagtgcgcgtatgcttaggctgcgcgcgtataactgatcgatcgaa
acccgggcatgcccacgacgacacgatcgactcgctagtgcgcgtatgct
gatgctagacgtaggctgcgcgcgtataactgatcgatcgaaacccgggc
atgcccacgacgacacgatcgactcgctagtgcgcgtatgctgatgctag
acggcttaggctgcgcgcgtataactgatcgatcgaaacccgggcatgcc
cacgacgacacgatcgactcgctagtgcgcgtatgctgatgctagacggc
ttaggctgcgcgcgtataactgatcgatcgaaacccgggcatgcccacga
cgacacgatcgactcgctagtgcgcgtatgctgatgctagacg
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Homology

• You can also find the same gene in a different
  plant (or even animal) by using a DNA word
  search IF you know the sequence
• - this is using a tool called BLAST (a simple
  comparing program).
• Similarity between genes in organisms is termed
  synteny. Otherwise known as comparative genomics.

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Why look at mutants ? and how would you
recognise one ?
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Normal
Cabbage
Ivy-like
Broccoli
How would you unambiguously describe these
mutants ?
Rose-like
Tree-like
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Normal flower
What happens when you ADD Ap-1 to an ordinary
plant ? ..The plant matures more quickly
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Practical
http//arabidopsis.info/students/