Genetics is the study of heredity. Whenever we talk about gene expression we only include the sequences that suffer the transcription process (genes itself). Genes are regulated by regulatory elements: promoters, enhancers, insulators, etc. These sequences are not always part of other coding sequences (like lnc-RNAs). This sequences are also inherited, and they also play an important role in gene expression, thus phenotype. Why is the gene the smallest unit of heredity? repetitive sequences or elements are also inherited, and also contribute to regulation of gene expression by it's more like structural role in the nucleus. The gene by itself will not transcribe without a promoter. Why aren't the DNA molecules considered the smallest units of heredity? Or otherwise, why isn't the gene with it's most simple (or perhaps their most needed) regulatory elements considered the smallest units of heredity?
Why are the regulatory DNA elements, structural DNA elements, and other forms of heredity excluded from the definition?
Finally, is there a point on still talk about "smallest units of heredity" in textbooks and elsewhere nowadays with the incredibly sensitive and/or massive technologies - that increases our knowledge to the point in witch we realize that DNA molecules are comprised of a lot of interesting non-gene stuff - tell us that heredity is indeed a ver complex and integrated process to have actually have a "smallest unit"?
Sorry about my english, I'm very young and stupid xD -as we all- ! I'd like to get some other and more complete answers that of a textbook.