Genetics 101 | National Geographic

• [Narrator] Genetics helps us understand the biological programming behind all life forms. But what exactly is the science of genetics? And what does its future hold?

Genetics is the study of heredity. The expression of traits and how they are passed from generation to generation. For thousands of years, humans have observed this inheritance of traits and implemented their knowledge to breed and domesticate plants and animals.

However, the science behind inheritance was only starting to be understood in the mid-19th century. Around 1865, Austrian monk and botanist, Gregor Mendel, published the results of his hybridization studies of pea plants. In his findings, he noted the role of factors that influence the expression of traits. These factors later became known as genes.

Each human has between 20,000 and 25,000 genes. This collection called a genome determines a person's traits by influencing factors on a cellular level. Genetic information is stored in every cell's nucleus. Structures called chromosomes carry this information in the form of deoxyribonucleic acid or DNA.

DNA is a double helix of nucleotides, chemical compounds composed of sugar and phosphate molecules along with the bases thymine, adenine, guanine, and cytosine. These segments of DNA are what we call genes, and it is within those genes that chemical compounds provide the coding for all information about a person's inherited traits.

Human cells contain so much DNA to carry this large amount of information that if unraveled, the DNA in each cell would be over six feet long. At the turn of the 21st century, an international effort to decode human DNA was launched called the human genome project; it ended up identifying about 99% of the entire human genetic sequence.

Discoveries in genetics research have unearthed tremendous opportunities in medicine such as genetic testing and the manipulation of genes. But with these opportunities come risks and ethical questions, and finding the answers to those questions may be the next stage of our understanding of genetics.