<P> In a DNA double helix, each type of nucleobase on one strand bonds with just one type of nucleobase on the other strand . This is called complementary base pairing . Here, purines form hydrogen bonds to pyrimidines, with adenine bonding only to thymine in two hydrogen bonds, and cytosine bonding only to guanine in three hydrogen bonds . This arrangement of two nucleotides binding together across the double helix is called a Watson - Crick base pair . Another type of base pairing is Hoogsteen base pairing where two hydrogen bonds form between guanine and cytosine . As hydrogen bonds are not covalent, they can be broken and rejoined relatively easily . The two strands of DNA in a double helix can thus be pulled apart like a zipper, either by a mechanical force or high temperature . As a result of this base pair complementarity, all the information in the double - stranded sequence of a DNA helix is duplicated on each strand, which is vital in DNA replication . This reversible and specific interaction between complementary base pairs is critical for all the functions of DNA in living organisms . </P> <Table> <Tr> <Td> </Td> </Tr> </Table> <Table> <Tr> <Td> </Td> </Tr> </Table> <P> The two types of base pairs form different numbers of hydrogen bonds, AT forming two hydrogen bonds, and GC forming three hydrogen bonds (see figures, right). DNA with high GC - content is more stable than DNA with low GC - content . </P>

How does the structure of a dna molecule help it store large amounts of information