Give scientific reasons: Both the strands of $DNA$ are not copied during transcription.

(N/A) If both the strands of $DNA$ were copied during transcription,two different $RNA$ molecules with complementary sequences would be produced.
These two complementary $RNA$ molecules would base-pair with each other to form a double-stranded $RNA$ $(dsRNA)$ molecule.
This $dsRNA$ would prevent the translation process,as ribosomes cannot translate double-stranded structures into polypeptides.
Furthermore,if one segment of $DNA$ were to code for two different polypeptides,the genetic information machinery would become highly complex and ambiguous,leading to conflicting protein synthesis.