Final answer:
A gene is a segment of DNA that carries the code for making a specific polypeptide chain. Genes determine the expression of physical characteristics and traits. Genes are located on chromosomes and are transcribed and translated into proteins.
Step-by-step explanation:
A gene is a segment of deoxyribonucleic acid (DNA) that carries the code for making a specific polypeptide chain. Genes are the basic units of heredity, passed from parent to child, and are responsible for the expression of particular physical characteristics or traits.
The sequence of nucleotides in a gene determines the order of the amino acids in a protein. Each gene contains a specific sequence of nucleotides that is transcribed into a complementary sequence of messenger RNA (mRNA), which is then translated into a polypeptide chain.
Genes are located on chromosomes, which are structures made of DNA and proteins. There may be hundreds or even thousands of genes on a single chromosome. The genes on a chromosome are organized into units called codons, which are three-letter codes that specify a particular amino acid in the protein sequence.