DNA Basics
You’ve heard terms like genes, DNA, and chromosomes. But what do these words mean exactly? Are they the same? Use this article to help you understand the relationship between these fundamental terms before studying genetic inheritance in more detail.
What Is DNA?
DNA (deoxyribonucleic acid) carries the genetic information in the body’s cells. A DNA molecule has two strands, which weave around each other in a shape like a twisted ladder, known as a double helix. Along each strand of the double helix, DNA is made up of four similar chemicals, called bases, that are repeated over and over in pairs. These pairs make up the “steps” of the ladder and follow a specific pattern of matching. The bases adenine (A) and thymine (T) always pairs together, while the bases cytosine (C) and guanine (G) always pair together.
What Is a Gene?
A gene is a specific section or distinct portion of a cell’s DNA. Genes are coded instructions for making proteins, the macromolecules that control the overall structure and function of the body. Human beings have about 25,000 to 40,000 genes, each with different lengths of code. Researchers have discovered what some of our genes do, but there are many genes whose functions are still unknown. What is known, however, is that genes are passed from one generation to another, causing the physical traits of offspring to represent those of their parents.
What Are Proteins?
Proteins are chains of chemical building blocks called amino acids. A protein could contain just a few amino acids in its chain or it could have several thousands. Proteins form the basis for most of what the body does such as digestion, making energy, and growing. Since DNA contains genes, and genes provide the instructions for making certain proteins, DNA is considered the “blueprint” of life.
What Are Chromosomes?
If you were to take all of the DNA out of one of your cells and stretch it from end to end, it would be approximately six feet long! It should be obvious that a molecule the size of an average human cannot fit inside of a human cell. Therefore, in order to fit within a cell, DNA is tightly packaged in bundles called chromosomes. Humans have 23 pairs of chromosomes (for a total of 46) inside of the nucleus of each cell. Of those, one pair is the sex chromosomes, which determine whether you are male or female. The other 22 pairs are autosomal chromosomes, responsible for determining the rest of your body’s makeup.
What Is the Human Genome?
The human genome is a complete copy of the entire set of human gene instructions. The Human Genome Project, completed in 2003, identified all the human genes in DNA and stored the information in databases so all researchers everywhere could use it.