Introduction: Human DNA & Genome

 The human DNA genome is the complete set of instructions that tells our body how to grow, develop, and function. These instructions are stored in a molecule called DNA (Deoxyribonucleic Acid), which is found in nearly every cell of our body.

DNA looks like a twisted ladder, called a double helix, and it is made up of four chemical "letters": A (adenine), T (thymine), C (cytosine), and G (guanine). These letters are arranged in a long sequence, and the order in which they appear determines everything from the color of our eyes to how our cells work.

Humans have 23 pairs of chromosomes (a total of 46), which are like books full of DNA. Each chromosome contains genes, which are short sections of DNA that give instructions to make proteins. These proteins do most of the work inside our bodies.

entire human genome contains about 3 billion DNA letters. Although only a small part of it directly makes proteins, the rest helps control how and when genes work.

Scientists mapped the human genome through a big international project called the Human Genome Project, completed in 2003. This has helped us understand diseases better and opened new doors in medicine and biology.

History of the Human Genome

Discovery of DNA (1869–1950s)

In 1869, Swiss scientist Friedrich Miescher first identified DNA.

In 1953, James Watson and Francis Crick, with the help of Rosalind Franklin’s X-ray images, discovered the double helix structure of DNA.

Understanding Genes and Heredity (1900s–1970s)

Scientists learned that genes are made of DNA and carry instructions for building proteins.

The genetic code—how DNA sequences make proteins—was cracked in the 1960s.

•Start of Genetic Mapping (1980s)

Scientists began creating maps of human chromosomes, locating genes, and understanding genetic diseases.

•The Human Genome Project (1990–2003)

An international scientific effort launched in 1990 with the goal of sequencing the entire human genome.

By 2003, the project was completed, revealing around 3 billion base pairs and identifying all about 20,000–25,000 genes in human DNA.

•Post-Genome Era (2003–Now)

New technologies like next-generation sequencing made genome sequencing faster and cheaper.

Scientists now study how genes interact with each other and with the environment (epigenetics).

Genome knowledge is used in medicine, forensics, ancestry testing, and personalized treatments.