A method to make libraries of hybrid polynucleotide molecules of two parental polynucleotide molecules utilizing single-stranded DNA was invented. Example of the method comprises several steps: (i) preparation of two single-stranded polynucleotide molecules comprising sequences containing one or more parts of homology and one or more parts of heterology, (ii) random or non-random fragmentation of said polynucleotides, (iii) hybridization of the fragmented molecules followed by de novo polynucleotide synthesis (i.e. polynucleotide chain elongation) on the hybridized molecules, (iv) separation of the chain elongation products (i.e. double-stranded polynucleotide molecules) into single-stranded polynucleotide molecules (denaturation) (v) hybridization of the resultant single-stranded polynucleotide molecules followed by de novo polynucleotide synthesis on the hybridized molecules, and (vi) repeating at least two further cycles of steps (iv) and (v).