Examples of Purines and Pyrimidines in DNA

📚 Quick Study Guide

• 🧬 Purines and pyrimidines are nitrogenous bases that form the building blocks of DNA and RNA.
• ⚗️ Purines are Adenine (A) and Guanine (G), characterized by a double-ring structure.
• 🔬 Pyrimidines are Cytosine (C), Thymine (T) (in DNA), and Uracil (U) (in RNA), characterized by a single-ring structure.
• 🧩 In DNA, Adenine (A) always pairs with Thymine (T), and Guanine (G) always pairs with Cytosine (C). This is known as complementary base pairing.
• 🧪 The base pairing is stabilized by hydrogen bonds: A-T has two hydrogen bonds, while G-C has three hydrogen bonds.
• 🔢 The general structure of DNA involves a sugar-phosphate backbone with these nitrogenous bases attached.

Practice Quiz

1. Which of the following is a purine base found in DNA?
   1. Adenine
   2. Cytosine
   3. Thymine
   4. Uracil
2. Which of the following is a pyrimidine base found in DNA?
   1. Guanine
   2. Adenine
   3. Cytosine
   4. Xanthine
3. In DNA, adenine pairs with which base?
   1. Guanine
   2. Cytosine
   3. Thymine
   4. Uracil
4. How many hydrogen bonds are formed between guanine and cytosine in DNA?
   1. 1
   2. 2
   3. 3
   4. 4
5. Which base is NOT typically found in DNA?
   1. Adenine
   2. Guanine
   3. Cytosine
   4. Uracil
6. Which of the following describes the structure of purines?
   1. Single-ring structure
   2. Double-ring structure
   3. Triple-ring structure
   4. No ring structure
7. Which of the following is an example of a correct base pairing in DNA?
   1. A-G
   2. C-T
   3. A-C
   4. A-T