map based clonong

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MAP BASED CLONING

• SUBMITTED BY
• SAMIA ABID
• M.Phil. Scholar

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These steps can be summarized as
follows Identify a marker tightly linked to
your gene in a "large" mapping population Find
a YAC or BAC clone to which the marker probe
hybridizes Create new markers from the
large-insert clone and determine if they
co-segregate with your gene
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If necessary, re-screen the large-insert
genomic library for other clones and search for
co-segregating markers Identify a candidate
gene from large-inset clone whose markers
co-segregate with the gene Perform genetic
complementation (transformation) to rescue the
wild-type phenotype Sequence the gene and
determine if the function is known
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If you do not have a transformation system for
your species of interest, the confirmation is
much more difficult. The most powerful approach
in this case is recombinational or mutant
analysis. Lets say you have two mutants in your
gene. You could cross these two mutants and
search a large segregating population for an
individual with a restored normal phenotype.
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Next you would clone from each of these three
individuals (the two mutants and the restored
line) homologues sequences that you feel contains
the correct gene. If you can show that the
restored line contains the same sequence as your
predicted gene ,
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and that the two mutants have unique changes in
the gene sequence not found in the normal gene,
you have obtained compelling evidence that the
putative sequence is indeed your gene of interest.
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