The section of DNA being used to make the strand of mRNA is known as the transcription unit.
Transcription units are base sequences of DNA that make up a single mRNA molecule during the process of transcription.
During gene expression, genes are first transcribed to genetic codes in mRNA molecules before being translated to their respective proteins.
Each unit of transcription represents a gene along with non-coding base sequences in DNAs, otherwise known as introns.
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