what are genes and what are they made of?

Genes are sections of DNA that act like instruction sentences, telling cells how to build and run the body, from eye color to how organs work. They are made of deoxyribonucleic acid (DNA), a long molecule built from four chemical “letters” called nucleotides: adenine (A), thymine (T), cytosine (C), and guanine (G).

What genes are

Genes are the basic units of heredity that parents pass down to their children. They carry coded information that helps determine traits such as appearance, some aspects of health risk, and how the body’s cells function.

• Each gene is a specific stretch of DNA with a meaningful “message” for the cell.

• Humans have on the order of 20,000–25,000 genes spread across their chromosomes.

• Some genes code for proteins, while others help control when, where, and how strongly those protein‑coding genes are used.

When a gene is “turned on,” its DNA instructions are copied into RNA and then used to build proteins that do most of the work in cells, like enzymes, structural components, and signaling molecules.

What genes are made of

Genes are made of DNA, and DNA itself has a clear chemical structure. At the smallest level, genes are built from repeated units called nucleotides, arranged in a specific order along the DNA strand.

• Each nucleotide has:
  • A sugar molecule (deoxyribose)
  • A phosphate group
  • One of four bases: A, T, C, or G

• The DNA molecule forms a double helix, like a twisted ladder, where A pairs with T and C pairs with G along the “rungs.”

• The particular sequence of these bases within a gene is what encodes the instructions for a specific RNA or protein.

Inside cells, DNA (and therefore genes) is packaged into larger structures called chromosomes, which are stored in the cell nucleus and wrapped around proteins called histones to help organize and regulate access to the genetic code.