Final answer:
The typical human gene does generally specify just one polypeptide, making the statement true. This is a foundational concept in molecular genetics, although there are notable exceptions.
Step-by-step explanation:
Originally, scientists proposed the "one gene-one enzyme" hypothesis, but it has been revised to the "one gene-one polypeptide" hypothesis to account for genes that code for polypeptides, rather than enzymes. Although some genes code for other molecules like tRNAs or rRNAs, in many cases, particularly in microbes, the hypothesis holds true. In fact, the discovery by Beadle and Tatum linking genes to specific polypeptides won them the Nobel Prize and is foundational to molecular genetics.
Moreover, the genetic code within DNA dictates the sequence of amino acids in a polypeptide. In eukaryotes, this relationship is more complex due to processes like splicing, which can result in multiple proteins from a single gene. For instance, a single nucleotide change can drastically affect the resulting polypeptide, as seen in the genetic disease sickle cell anemia where a single amino acid substitution in the hemoglobin protein causes significant structural changes in red blood cells.
In summary, while the concept of "one gene, one polypeptide" is not absolute, as there are exceptions, it is broadly accurate across many organisms, reflecting the complexity and variability in genetic expression and protein synthesis.