Genes and DNA Carry the Instructions for Traits

Hey there — I am Medi, and today we are going inside a living cell to read the instructions of life. Inside almost every cell in your body is a nucleus, and coiled up inside that nucleus is DNA — deoxyribonucleic acid. DNA is shaped like a twisted ladder called a double helix. The rungs of the ladder are made of pairs of chemical bases: adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). The order of these bases along the ladder is like a molecular alphabet that spells out instructions. A gene is a specific stretch of that DNA ladder — usually hundreds to thousands of base pairs long — that contains the instructions for building one protein. Think of DNA as a giant recipe book, and each gene is one recipe. Proteins are the real workers. Once a gene's instructions are read, your cell builds the matching protein. Proteins do almost everything: they form the structure of your hair and skin, carry oxygen in your blood, and control chemical reactions throughout your body. The enzyme tyrosinase, for example, converts a building block called tyrosine into melanin — the pigment that colors your hair and eyes. More active tyrosinase means more pigment. Because proteins do so much, the genes that code for them shape your traits — observable characteristics like eye color, blood type, or the shape of your earlobes. Different versions of the same gene (called alleles) can produce slightly different proteins, which is why two people can have the same gene for hair color but end up with different shades. Here is the key chain to remember: DNA sequence → gene → protein → trait. Every link matters.