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One way is experimentation. And because people change, environment change and they are more convenient
Answer: DNA is antiparallel because Its double strands run in opposite directions.
Explanation: The antiparallel nature of DNA strands means that as one strand runs in 5'->3' direction, the other strand runs in 3'->5' direction. The two antiparallel DNA strands are not identical in either base sequence or composition rather they are complementary to each other. This means that anywhere thymine base is found in one strand, adenine is present in the other strand and anywhere guanine occurs in one strand, cytosine occurs in the other strand.
1/ leaves because its fall 2/ idkk stop being lazy :)
I am pretty sure number 4 is your answer