Plant Genome I Conference
Town & Country Conference Center, San Diego, CA, November, 1992.
PG-I: 90pg1
COMPARISON OF RAPD MAPS FOR TWO SETS OF MAIZE
RECOMBINANT-INBRED LINES.
Mitrick A. Johns, Department of Biological Sciences, Northern
Illinois University, DeKalb, IL 60115.
The TXCM and COXTx recombinant-inbred maize lines (Burr et
al., 1988) were analyzed by the RAPD gene-mapping technique
(Williams et al., 1991) using 100 10-mer primers. A total of 290
polymorphic bands were mapped, with loci found on all chromosomes
in numbers roughly proportional to the chromosome lengths. Most
of the bands segregated in the expected 1:1 ratio for
presence/absence, indicating that cases of two unlinked bands
having similar sizes are quite rare. A band that is polymorphic
in one cross is usually not polymorphic in the other cross; such
a band is about equally likely to be monomorphic in the other
cross as it is to be absent in both parents of the other cross.
Bands of similar size (on agarose gels) in the two crosses
usually map to different, unlinked locations. This results in
very different genetic maps for the two crosses. At least for
maize, maps based on RAPDs may not be very useful when different
lines need to be compared. --RAPD primers hybridize to short
inverted repeats in DNA, sequences that are also found on the
ends of many plant transposable elements. A few primers generate
"stray" bands, found in some progeny lines but in neither parent.
These stray bands may result from genetic rearrangements in
active transposable elements, but their rarity suggests that
active transposable elements will not affect most RAPD mapping.
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