AP BIOLOGY

Detailed explanation-1: -Each molecule of messenger RNA (mRNA) is a transcribed copy of a gene that is used by a cell for synthesizing a polypeptide chain.

Detailed explanation-2: -By definition, exons and introns are sequences in a protein-coding gene region of a double-stranded DNA molecule (dsDNA) that are expressed as proteins, or intervening sequences not so expressed.

Detailed explanation-3: -One gene codes for one mRNA molecule, which codes for one polypeptide. This is known as the central dogma of molecular biology.

Detailed explanation-4: -An exon is a coding region of a gene that contains the information required to encode a protein. In eukaryotes, genes are made up of coding exons interspersed with non-coding introns. These introns are then removed to make a functioning messenger RNA (mRNA) that can be translated into a protein.