Problem : Name the four DNA bases. Which two are purines? pyrimidines?The four bases are adenine, cytosine, guanine, and thymine. Purine bases are adenine and guanine. Pyrimidine bases are cytosine and thymine.
Problem : Which position on purine bases binds to the ribose? On pyrimidines?Purine bases bind from their 9' nitrogen to the ribose group. Pyrimidine bases bind from their 1' nitrogen.
Problem : Why is the DNA sugar group called a "deoxyribose"? What group is the DNA ribose group missing and at what position?The DNA sugar group is called a deoxyribose, instead of a ribose, because it lacks an -OH group at its 2' position.
Problem : What force holds complementary base pairs together?Hydrogen bonds between hydrogen bond donors and acceptors on each base.