Final answer:
Genes are the basic molecular units that enable hereditary information to be transmitted from parent to offspring. They contain instructions for building proteins, which determine an organism's traits.
Step-by-step explanation:
The basic molecular unit that enables hereditary information to be transmitted from parent to offspring is genes. Genes are segments of DNA that contain instructions for building proteins, which ultimately determine an organism's traits. Hereditary information is stored in the genetic code of DNA, which is passed down from parent to offspring.