Structure of DNA
Purine and pyrimidine nucleotides are the building
blocks of DNA. Adenine specifically binds to thymine
with 2 hydrogen bonds and cytosine specifically binds to
guanine with three hydrogen bonds. Hydrogen bond is a
type of attractive intermolecular force that exists
between two partial electric charges of opposite
polarity. Two strands of DNA are anti parallel with
major and minor grooves.
DNA replication
The process of making an identical copy of a section of duplex DNA,
using existing DNA as template for the synthesis of new DNA strands.
DNA undergoes semi conservative nature of replication. There are
three steps in the replication process: Initiation, elongation and
termination. Initiation always begins at the origins of replication,
it is bidirectional with most genomes and priming is with RNA.
Elongation has three steps: unwinding of DNA, relieving of torsional
stress and polymerization of poly nucleotide chain. One strand of
DNA is made continuously while the other strand is synthesized in
fragments.
Functions and structures of DNA
replication enzymes
Many enzymes are involved in DNA replication such as topoisomerase,
helicase, primase, DNA polymerase and ligase. Topoisomerases relax
the super coiling of DNA, helicases unwind double strand of DNA,
primases synthesize a primer, DNA polymerases add and read proof new
bases and ligases link the added bases.
