From the rules of base pairing, we know that Adenine always pairs with Thymine, and Cytosine always pairs with Guanine.
Adenine is denoted as A
Thymine is denoted as T
Cytosine is denoted as C
Guanine is denoted as G
Therefore if the base sequence is TCAAGT, then following the rule of base pairing, the complementary sequence to this will be AGTTCA
This strict arrangement is because only with this arrangement can hydrogen bonds form between these base pairs. Any other arrangement cannot sustain the integrity of the molecule.
