Chapter 15, Problem 6STP

Summary Introduction

Introduction :

Erwin Chargaff, a biochemist proposed a rule called Chargaff’s rule that states that the amount of the purine bases are equal to pyrimidine bases. Therefore, the amount of adenine is equal to the amount of thymine, and the amount of cytosine is equal to the amount of guanine.

Answer to Problem 6STP

Correct answer :

The correct answer is option (A) base pairing

Explanation of Solution

Explanation/justification for the correct answer :

Option (A) base pairing. According to Chargaff, during replication of DNA, base pairing is in specific manner. Adenine (A) always pairs with thymine (T) and cytosine (C) always pairs with guanine (G). Thus, this is the correct answer.

The explanation for the incorrect answer :

Option (B) helix formation. DNA double helix is formed from two complementary strands of nucleotides held together by hydrogen bonds between G-C and A-T base pairs. Thus, this is an incorrect option.

Option (C) alternation of deoxyribose and phosphate. Each DNA strand has a backbone made of alternating deoxyribose and phosphate. Thus, this is an incorrect answer.

Option (D) placement of 3´ and 5´carbons. DNA molecule are called 3' and 5' ends, based on the numbering of carbon atoms in deoxyribose sugars. Thus, this is an incorrect answer.