What is a gene? Explain its structure and function.

(N/A) gene is defined as the functional unit of inheritance. It is a segment of $DNA$ that codes for a polypeptide.
$1$. $A$ gene is also defined by the $DNA$ sequence that codes for $t-RNA$ or $r-RNA$ molecules.
$2$. The $DNA$ segment within a transcription unit that codes for a polypeptide is called a cistron. In eukaryotes,genes are monocistronic,whereas in prokaryotes,they can be polycistronic.
$3$. Eukaryotic genes are 'split genes' containing interrupted coding sequences. The coding or expressed sequences are called exons.
$4$. Exons appear in mature or processed $RNA$ and are interrupted by introns. Introns do not appear in mature or processed $RNA$.
$5$. The inheritance of a character is also affected by promoter and regulatory sequences of a gene. Regulatory sequences do not code for any $RNA$ or protein but control the expression of structural genes.