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To characterize the molecular properties of RAPD variation in Pinus sylvestris (L.), we isolated 10 polymorphic and 10 monomorphic RAPD fragments and used them as probes in Southern analysis of the RAPD profiles and genomic DNA digests of P. sylvestris individuals from different populations. The results showed that: (i ) individual RAPD bands often contain more than one non-homologous DNA sequence, though one sequence usually predominates; (ii ) Southern hybridization revealed that the presence/absence polymorphism of RAPD bands is due to the lack of amplification of the corresponding sequence rather than to the absence of the target sequence in the individuals lacking the band; (iii ) despite of a large genome in conifers, most of the analysed RAPD fragments did not appear to originate from repetitive sequences. Of the 20 RAPD fragments tested, only one fragment appeared to be of repetitive origin. The implications of the observed molecular properties of RAPD variation for genetic analysis are discussed.
Key words: Pinus sylvestris, RAPDs, sequence homology, repetitive sequence, presence/absence polymorphism
by Alfred E. Szmidt