image
Figure 2–47. Minor, i.e. rare pyrimidine (A) and purine (B) bases found in DNA.
The study of the kinetics of DNA renaturation in different organisms
has shown that in the different fractions it takes place in inverse proportion
to the complexity of the sequences. The greater rate of renaturation of the
individual fraction is due to the fact that it consists of nucleotide sequences
that are multiply repeated. When the renaturation process takes place at a
lower rate, the nucleotide sequences are assumed to be unique or
unrepeated. Literature data show that the sizes of the fractions with
repeated sequences can differ considerably — from 5 to 80% (an average
of 30—40%), as about 50 to 60% of the genome of the studied organisms
consisting of repeated nucleotide sequences of an average length of 300
nucleotide pairs that are intermittently replaced by unique sequences of a
length of 700 to 1100 nucleotides (see Hadjiolov et al., 1976). Except the