Marker conversion

- For information about different markers, please refer to the chapter on Markers -

There are situations where markers need to be converted into other types of markers:

  1. Some older types of markers are not high-throughput, and cannot be efficiently applied in breeding.
  2. When a diagnostic marker in one mapping population is not polymorphic in other material.

How does it work?

The exact procedure to convert markers goes beyond the scope of this course, but an example is given below that will mention several necessary steps. The method is also used for convert gene sequences into convenient markers.
To convert RAPD or AFLP marker or a gene sequence into a SNP marker for use in MAS we need to:

  • Amplify the gene sequence of the two parents, or:
  • Clone the RAPD or AFLP band as follows:
    • cut out the band from the gel
    • extract DNA from that part of the gel
    • clone the DNA into a vector and transform into Escherichia coli
  • Sequence the DNA of the amplified fragment
  • Compare the sequences to find one or more SNPs between the parents, flanked by a large number (about 50) non-polymorphic base pairs.
  • The SNP and the flanking sequences are used to run SNP markers on progeny from the cross.

Summary

→    For use in practice, markers need to be converted into markers that are highly reproducible, easy to use, quick and cheap.

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