Choose the best, or most specific, term to complete each sentence. A (an) is a segment of a gene that does not code for a product. A (an) is a DNA sequence that begins with a start codon and ends with a stop (nonsense) codon. A (an) is a DNA segment that is transcribed and processed to produce a specific protein or RNA product. A (an) is a gene segment that appears in mature mRNA. A (an) is a small cDNA sequence, synthesized from mRNA and sequenced, that can be used to identify a particular gene. A (an) contains genes for related proteins and regions that function in gene transcription.