Final answer:
The complementary DNA strand to the sequence TCAGAT is AGTCTA, with base pairing rules A-T and C-G.
Step-by-step explanation:
The sequence on the complementary strand of DNA for the given sequence TCAGAT is AGTCTA. In DNA, adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G). Therefore, for each T in the given sequence, there will be an A in the complementary strand, for each C an G, for each A a T, and for each G a C.