Random Amplified Polymorphic DNAs - RAPDs,Oligonucleotides

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	Random Amplified Polymorphic DNAs - RAPDs - RAPDs are generated by using random sequence ten bases oligonucleotides (at least 50% G + C and lacking inverted repeats) as primers for PCR amplification of genomic DNAs from different strains/species (Appendix-4.llI). Polymorphism is detected as the presence/absence of an amplification product (≡band). For example, an amplification product is detectable as a band in strain A, while strain B does not show the product; this, however, is the ideal situation. In practice, each strain yields more than one band, and some of them may show polymorphism.
The F1 hybrid between the two strains (A x B) will show the band, while in F2 a 3:1 ratio will be obtained. Thus RAPDs behave as dominant markers; the presence of amplification product may be regarded as the dominant allele, say A, and its absence as the recessive allele a. Thus RAPD markers can be regarded in the same manner as RFLP markers and similarly used for preparation of RAPD maps. RAPD maps have been prepared for several crop species like maize, tomato, soybean, rice, sugarcane, sunflower etc. RAPDs have similar applications as RFLPs but are more rapid and convenient. In some cases, RAPDs may generate information in 4 weeks, which would take about 2 years to obtain using RFLPs.