Answer;
-Gene
A specific stretch of DNA that codes for the amino acid sequence of a polypeptide is called a gene.
Step-by-step explanation;
-A gene is the basic physical and functional unit of heredity. Genes are made up of DNA.
-Each gene occupies a specific position on a chromosome. Because genes provide instructions for making proteins, and proteins determine the structure and function of each cell in the body, it follows that genes are responsible for all the characteristics you inherit.