describe in little paragrahs what happens with the NGS method for dna sequencing and the sanger method
NGS (Next-Generation Sequencing) method is a technique used for rapid and parallel sequencing of multiple DNA fragments. In this method, a DNA sample is initially fragmented into smaller pieces, which are then attached to a solid surface, forming a DNA library. The library is then subjected to a series of steps, including amplification and sequencing reaction.
During the sequencing reaction, each DNA fragment is individually replicated and labeled with fluorescent markers. The fragments are then loaded onto a sequencing machine, where they pass through a nanoscale pore and the fluorescence signals are recorded. By comparing the order and intensity of the fluorescence signals, the machine analyzes and determines the sequence of the DNA fragment.
On the other hand, the Sanger method, also known as the dideoxy chain termination method, was one of the earliest techniques developed for DNA sequencing. In this method, the key component is the use of modified DNA nucleotides called dideoxynucleotides (ddNTPs). These ddNTPs lack a 3'-OH group, which prevents further extension of the DNA chain.
During the Sanger sequencing process, a DNA sample is divided into four separate reactions, each containing a mixture of regular DNA nucleotides (dNTPs) and a specific ddNTP. As DNA replication occurs, the incorporation of the ddNTPs randomly terminates each chain at different points. This results in the generation of a set of labeled DNA fragments of varying lengths, which are then resolved using gel electrophoresis.
The fragments are separated based on their size, from which the sequence is deduced by reading the banding pattern. By analyzing the bands in each reaction, the sequence of the original DNA sample can be determined. However, the Sanger method is slower and less cost-effective in comparison to NGS, which has revolutionized DNA sequencing with its high-throughput capabilities.