The purpose of this web site is to provide an introduction to the most important and basic concepts of Molecular Biology and Genetics. All life begins with DNA, and so will we!

What is DNA?


DNA stands for Deoxyribonucleic Acid (de-oxy-ryeboh-nuclay-ik acid). DNA is often referred to as the "blueprint of life" because it contains all the information needed to make every protein of every cell in your entire body. Proteins make up our hair, skin, nails, and muscles. Proteins are also essential to cell function. Without the information provided in DNA, there would be no complex life!

The Structure of DNA

In the 1950's, James Watson and Francis Crick proposed the famous double helix model for DNA. Their model gained acceptance in the scientific community after supporting research from Rosalind Franklin. Her work in x-ray crystallography produced photographs that could only be made by such a structure.

The shape of DNA resembles a twisted ladder. Each side of the ladder, or backbone, of DNA consists of a repeating sequence of building blocks called "nucleotides". Every nucleotide consists of a phosphate, a sugar, and a nitrogen-containing base. DNA contains four different nitrogen-containing bases. These bases are listed in the table below.

Base Name Represented by:
Adenine A
Guanine G
Cytosine C
Thymine T
Base Pairing

Base Pairing Rules

Further experimentation by a scientist named Chargraff revealed that the four nitrogen-containing bases pair in a particular way. He looked at the amount of each base found in one cell. He found that the cell contained the exact same amount of Adenine and Thymine bases. It also contained the same amount of Cytosine and Guanine bases. From these results, he concluded that Adenine (A) will only pair with Thymine (T) and vice versa, while Cytosine (C) will only pair with Guanine (G) and vice versa. Using these base pairing rules, scientists can easily predict the make-up of a complementary strand of DNA if they are looking at a single strand (one side of the ladder). The image above illustrates how the bases of each nucleotide on one strand of DNA pair up with the complementary strand.

Try this:

Play the DNA sequencing game, and see how well you know your base pairing rules.
Click here to try it!

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