Denaturation and reassociation properties of the genome of Phaseolus vulgaris.

Phaseolus vulgaris genome was characterized by its thermal denaturation behaviour and reassociation kinetics. The melting pattern of the native DNA was biphasic revealing a minor high-melting and a major low-melting DNA component with tm values of 93.5 degrees C and 38.7 degrees C, respectively. Approximately 40% of the total sonicated DNA (550 nucleotide pairs) formed duplexes under cot 50 conditions and was considered to be repetitive. The cot 50 DNA had an average tm value of 79 degrees C. The cot 1 DNA, as the native DNA, had a biphasic melting pattern consisting of a minor high-melting DNA component and a major low-melting DNA component (the tm values being 92.5 and 78.7 degrees C). The optical hypocromicity data of the cot 1 DNA indicated the presence of one minor fast-reassociating and one major slow-reassociating component with their complexities as 1.1 x 10(3) and 2.1 x 10(5) nucleotide pairs respectively. The haploid genome size of Phaseolus vulgaris was estimated from the cot 1/2 value of its non-repetitive DNA as 3.3 x 10(8) nucleotide pairs or 0.36 pg.