The present disclosure relates to methods for constructing polynucleotide libraries and/or polynucleotide sequencing. Related kits and devices are also disclosed. The present disclosure also relates to compositions, kits, devices, and methods for conducting genetic and genomic analysis, for example, by polynucleotide sequencing. In particular aspects, provided herein are compositions, kits, and methods for constructing libraries with improved ligation efficiency and conversion rate during sequencing. In certain embodiments, the compositions, kits, and methods herein are useful for analyzing polynucleotide fragments, such as circulating polynucleotide fragments in the body of a subject, including circulating tumor DNA.