Final answer:
A gene is a sequence of DNA that contains the instructions for making a specific protein or polypeptide chain. Genes are fundamental units of heredity and directly influence the physical traits of an organism. Mutations in genes can result in genetic disorders and diseases.
Step-by-step explanation:
A gene is a segment of DNA that carries the code for making a specific polypeptide chain. This definition can be expanded to express that a gene is the basic physical and functional unit of heredity, and it is responsible for the transmission of traits from parent to offspring. The genetic code within the gene functions as a series of three-letter codes, each of which corresponds to a specific amino acid, the building blocks of proteins.
The process of gene expression starts with transcription, where a gene is copied into messenger RNA (mRNA). This mRNA is then used as a template for protein synthesis during translation. Each polypeptide chain can combine to form proteins, which carry out various critical functions in the body. If a protein is composed of more than one polypeptide chain, each chain is encoded by a different gene.
Importantly, changes or mutations within genes can lead to various genetic disorders, such as cystic fibrosis or certain forms of cancer, which are caused by mutations in genes that control cell division and can be inherited.