Save Answer Which of the following best describes a DNA molecule? contains ribose 1. double helix 2. made of amino acids 3. contains uracil 4. none of these 5.
The Correct Answer and Explanation is:
Correct Answer: 2. double helix
Explanation:
A DNA (deoxyribonucleic acid) molecule is best described as a double helix. This structure was first proposed by James Watson and Francis Crick in 1953. The double helix refers to the shape formed by two long strands of nucleotides that spiral around each other. Each strand is made up of smaller units called nucleotides, which are composed of three parts: a phosphate group, a deoxyribose sugar, and a nitrogenous base.
There are four types of nitrogenous bases in DNA: adenine (A), thymine (T), guanine (G), and cytosine (C). These bases pair in specific ways across the two strands. Adenine pairs with thymine, while guanine pairs with cytosine. These base pairs are held together by hydrogen bonds, forming the steps of the twisted ladder structure.
Option 1, “contains ribose,” is incorrect because DNA contains deoxyribose, not ribose. Ribose is found in RNA (ribonucleic acid), which is a different type of nucleic acid.
Option 3, “made of amino acids,” is incorrect because amino acids are the building blocks of proteins, not nucleic acids like DNA.
Option 4, “contains uracil,” is also incorrect because uracil is found in RNA. DNA uses thymine in its base pairing instead of uracil.
Therefore, the correct and most accurate description of DNA among the choices is “double helix.” This structure allows DNA to carry genetic information in a stable and compact form. It also explains how DNA can be copied accurately during cell division. Understanding this structure is essential to the study of genetics, biology, and molecular medicine.
