DNA, which stands for deoxyribonucleic acid, is commonly imagined as the ladder spirals that make you who you are. There are two different types that are named according to where they are located in your body. DNA is found in the nucleus of human body cells, therefore named nuclear DNA. When it is located in the mitochondria, it is known as mitochondrial DNA. However, what really makes you you is the information kept in the chemical bases adenine, cytosine, guanine, and thymine. Those bases match: adenine to thymine, and guanine to cytosine to form base pairs. Every chemical base is connected to a 5-carbon sugar molecule and one phosphate molecule, creating a nucleotide. All those nucleotides make up my, and your, DNA. (What) We know all of this now, but DNA wasn’t studied nearly as much in the past.
The idea was first proposed by Charles Darwin in 1859 with his controversial book you may have heard of: The Origin of Species. He wrote about his discoveries on the Galapagos Islands, where he observed various animals, such as finches, and how they each had slight variations on each island. On one island, the finches would have short, curved beaks, but on another, they would feature long, straight beaks. Darwin inferred that they evolved to better adapt and suit to their different environments and food sources in a process he called natural selection. This discovery is considered one of the founding ideas of DNA, genetics, and the concept of passing down genes and traits to offspring. Darwin collected all of his observations and discoveries into The Origin of Species. Although we accept it now, his writing was new and unknown to the minds of the people of his time.
Fast forward a few years to 1866, and another man began experiments testing the traits of pea plants. His name was Gregor Mendel, and although you might have never heard of this guy, he is known to many as the father of genetics. However, back when he was conducting his experiments, his research was not highly respected. In fact, his ideas were disregarded, only to be brought back up thirty four years later. Mendel’s experiments involved breeding different colored pea plants and observing the color of the offspring. He found that a green pea plant and a yellow pea plant resulted in all yellow peas. However, by the next generation, the ratio of yellow to green plants became 3 to 1. The yellow color trait was deemed ‘dominant’, and the green ‘recessive’. This phenomenon can be explained with a punnett square.
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A punnett square is basically a square divided into four equal parts. It was invented by a man named Reginald Punnett. Here’s how it works: the traits of the parents are placed on the edge of the square, with a capital letter representing dominant traits and a lowercase letter as a symbol for the recessive trait. Each child will receive one letter from each parent. The letters are combined, kind of like a multiplication table. For example, if an uppercase letter Y represents brown eyes, and a lowercase letter is blue eyes, then a double uppercase Y combination will result in brown eyes, and two lowercase y’s mean blue eyes are inherited. In the case of one capital Y and one lowercase y, the dominant trait, brown eyes, overrides and the offspring receives that trait.
Now that’s just one tiny aspect of the whole picture of DNA. If we zoom out from the little details that pinpoint each and every feature of us, we realize that there are 3.2 billion bases inside of us. Thus began the Human Genome Project, which was planned to take 15 years starting in 1990. That’s more than the amount of time I’ve spent on earth! The project charted the entire human genome and determined each and every letter that makes up our DNA. It actually took 13 years, ending in 2003, and despite the few errors it may contain, it helped scientists learn more about us.
