In DNA, purine bases bond with pyrimidine bases instead of other purines, and vice versa. Memorizing each nucleotide’s structure will be crucial for test day.Įach nucleotide follows strict rules for bonding with other nucleotides. It’s important to remember adenine and guanine still have differences in the organic structure: for instance, in the number of attached carbonyl (C=O) bonds and where they are located. Adenine and guanine are often broadly classified as purine nucleotides, while cytosine and thymine are classified as pyrimidine nucleotides. Adenine and guanine have purine bases, while cytosine and thymine have pyrimidine bases. Take a close look at the structure of nitrogenous bases of the nucleotides. Purines are made of two rings and are larger than pyrimidines, which contain only one ring. While both purines and pyrimidines are aromatic nitrogenous bases, they differ in size and ring structure. There are two classes of nitrogenous bases: purines and pyrimidines. The nucleotides have different nitrogenous bases. In contrast, nucleosides are molecules that only consist of a nitrogenous base and a pentose sugar. Each nucleotide consists of a phosphate group (PO4-), a nitrogenous base, and a pentose sugar that links the other two groups together. What do each of these four nucleotides have in common? All of the bases have a very similar structure. Throughout this guide, you will also see bolded terms that will be important to recall on the exam. It’s helpful to create a list outlining why each component or modification of DNA is necessary for its function. When studying DNA, it’s easy to confuse the names of the bases and building blocks of DNA as well as the different modifications DNA undergoes in the cell. This guide will take a tour through the structure and function of DNA and what can go wrong. As a result, proper DNA regulation is vital to cell survival. Errors in DNA replication can vary significantly, from unnoticeable mutations to life-threatening illnesses, such as cancer. DNA is carefully replicated and inherited from one generation of cells to the next to avoid any errors. DNA stores and selectively expresses the genetic information our cells need to function. DNA, or deoxyribonucleic acid, is one of the two main molecules of nucleic acids (the other being RNA, or ribonucleic acid). Understanding DNA and its function is crucial on the MCAT, especially as DNA is the biological basis of life.
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