What are the DNA segments that play a key role in hereditary transmission?

Genes are the fundamental units of heredity within DNA that carry the information necessary for the development, functioning, and reproduction of organisms. They are segments of DNA that contain the instructions for producing proteins, which play a critical role in determining an organism's traits and characteristics. Each gene can vary in form, which leads to the concept of alleles, representing different versions of a gene.

While chromosomes are structures that organize and carry genes, and chromatids are the duplicated forms of chromosomes, it is the genes themselves that are directly involved in the hereditary transmission process. Therefore, when discussing what specifically plays the key role in passing traits from one generation to the next, genes are the primary segments responsible for this transmission.