Only one strand of the double helix is used as template for transcription. How would the transcription machinery recognize the template strand for transcription of a particular gene? Is it necessary that this strand will be used as template for transcription of all genes of that particular organism?
The transcription machinery recognizes specific sequences on one strand of the double helix (promoter). These sequences determine the template strand. However, promoters can be located on both strands and genes in the genome of the particular organism can be transcribed from different DNA strands.