In a double stranded DNA which strand is transcribed. Why?

Dear student

The dsDNA has two strands of polarity 3′ → 5′ and  5′ → 3′ 

The strand with polarity 3′ → 5′ acts as a template (Template strand or non coding strand) and the RNA strand synthesised has complementary bases to this strand.

The strand with polarity 5′ → 3′ acts as coding strand (which is a misnomer since it does not code for anything). Coding strand has sequence similar to RNA formed after transcription except for the change that thymine is present instead of uracil.

Hence, in double stranded DNA coding strand with polarity 3′ → 5′ is transcribed as RNA polymerase can synthesise RNA i.e add nucleotides only in 5′ → 3′ to newly synthesised RNA. Thus, synthesising RNA with opposite polarity but complementary to template strand.

Regards