Sentence:  The process in which the DNA molecule unwinds, separates its two polynucleotide strands, and synthesizes an RNA molecule from one of these DNA strands is called <WSD>transcription.</WSD> Genes transcribe chemical messages in the form of RNA molecules. <WSD>Transcription</WSD> begins at some site in the DNA duplex and  ends at some other point. 
Meaning of the word marked with <WSD> tags:  The synthesis of RNA under the direction of DNA.