Purified dsDNA

The DNA molecule contains genetic information about the development and function of an organism, and in addition to carrying genetic information and playing a key role in biological processes, it has many applications in drug design, nanotechnology, etc. The core process of DNA involves replication and transcription, where proteins and RNA can be involved in regulating genetic information. DNA replication is initiated by DNA polymerase and begins with a localized opening of base pairs that separates the two strands from each other, and then the localized openings move along the strand like a Y-fork. The bases are matched to synthesize new paired strands, the leading and lagging strands. Another important phenomenon related to the opening of DNA base pairs is transcription, where DNA carrying information is transcribed into messenger RNA (mRNA) with the involvement of RNA polymerase, which is subsequently read and synthesized into peptide chains by ribosomes. RNA polymerase recognizes and attaches to transcription sites on double-stranded DNA, forming pre-initiation complexes and closing bases after transcription. This process is accomplished in a very coordinated manner at a rate of tens to a hundred base pairs per second.

The double helix structure of DNA has the following advantages. Genetic information is encoded twice in the two complementary strands, storing information and enabling error checking during replication; the sugar-phosphate backbone facilitates base pairing between the complementary strands, which is essential for the storage and retrieval of genetic information. The bases are arranged in lines or stacks along the longitudinal axis of DNA, allowing proteins to directly access sequence fragments; the reversible opening and closing of the two DNA strands enables replication and transcription without destroying the original molecule.

DNA double strands can be opened in vitro by heat melting, i.e., separating the two strands of DNA by raising the temperature of the solution containing the DNA molecule. In this process, the hydrogen bonds between the bases are broken and the two strands are separated from their helical structure. Another method that leads to separation is to pull on one of the DNA strands while leaving the other strand immobilized on a glass slide is called force-induced DNA melting. Although DNA denaturation in vitro is distinct from in vivo replication and transcription, understanding denaturation can provide a great deal of useful information for understanding the entire process.

Figure 1. Schematic representation of the melting curve of a short, homogeneous DNA chain
(Source: Singh A, et al. 2022)

Human double stranded DNA