Genes, proteins, and traits

Key points:

• Genes are specific stretches of a chromosome’s DNA molecule. DNA molecules are made up of smaller parts called nucleotides. So, a gene is a specific stretch of nucleotides within a chromosome’s DNA.
• DNA is made up of four types of nucleotides. These nucleotides are often called by their shortened names: A, C, T, and G (which stand for adenine, cytosine, thymine, and guanine). The nucleotides in a gene are connected in a specific order.
• Proteins are molecules that carry out many different functions in cells. For example, some proteins provide structure for the cell. Others help carry out chemical reactions.
• Proteins are made up of smaller parts called amino acids. The amino acids in a protein are also connected in a specific order. A protein’s amino acids determine its 3D structure and its function.
• The cell builds proteins using instructions found in genes. Specifically, the order of nucleotides in a gene determines the order of amino acids in one or more proteins.
• An organism has many different genes, and so can produce many different proteins. These proteins have functions that affect the organism’s traits.