Sequencing the genome
Sequencing involves breaking DNA into short fragments and determining their base sequences. There are two main methods: chain termination or by chemical cleavage. It allows genome-wide comparisons to be made between individuals using appropriate databases. This alows us to understand the role of a particular gene, and may suggest a relationship between different species.
A DNA nucleoside triphosphate (NTP) consists of deoxyribose, a nitrogenous base and three phosphate group. Only NTP's can be used in the replication of DNA. Loss of the two phosphates supplies the energy for the reaction.
In the chain termination method of sequencing DNA, fragments to be sequenced are produced by the use of four dideoxynucleoside triphosphates (ddNTPs). A ddNTP lacks a hydroxyl group, which is necessary for a DNA chain to continue growing. Inclusion of a ddNTP terminates growing DNA chain.
DNA is denatured to seperate its two strands. In the presence of an ample supply of each of the four NTP's, single-stranded DNA is replicated by DNA Polymerase, using a primer to begin the synthesis. A primer is a short length of single stranded DNA complementary to the base sequence at the 3' end of the chain. It forms a starting point from which DNA polymerase can continue replicating the chain.
A low concentration of one of…