Which of the following statements regarding DNA is false?
A. DNA molecules have a sugar-phosphate backbone.
B. DNA is a nucleic acid.
C. One DNA molecule can include four different nucleotides in its structure.
D. DNA uses the nitrogenous base uracil.
E. DNA uses the sugar deoxyribose.
The correct answer and explanation is:
The correct answer is D. DNA uses the nitrogenous base uracil.
Explanation:
DNA (Deoxyribonucleic Acid) is a molecule that carries genetic information essential for the functioning and reproduction of living organisms. It has a unique structure and specific components that distinguish it from other types of nucleic acids, like RNA.
- DNA molecules have a sugar-phosphate backbone (Statement A): This is true. DNA consists of a long chain of nucleotides, and each nucleotide is made up of a sugar (deoxyribose), a phosphate group, and a nitrogenous base. The sugar and phosphate groups form the backbone of the DNA strand, while the nitrogenous bases extend from the backbone.
- DNA is a nucleic acid (Statement B): This is true. DNA belongs to a class of molecules known as nucleic acids, along with RNA. Nucleic acids play a critical role in storing and transmitting genetic information in cells.
- One DNA molecule can include four different nucleotides in its structure (Statement C): This is true. DNA consists of four different nitrogenous bases—adenine (A), thymine (T), cytosine (C), and guanine (G). These bases pair specifically (A with T, C with G) to form the structure of the DNA double helix.
- DNA uses the nitrogenous base uracil (Statement D): This is false. Uracil is a nitrogenous base found in RNA, not DNA. In DNA, the base thymine (T) replaces uracil. While uracil pairs with adenine (A) in RNA, thymine pairs with adenine (A) in DNA. This is one of the key differences between RNA and DNA.
- DNA uses the sugar deoxyribose (Statement E): This is true. The sugar in DNA is deoxyribose, which is similar to ribose (the sugar found in RNA), but it lacks one oxygen atom, which is why it is called “deoxyribose.”
Therefore, the false statement is D. DNA does not use uracil, and instead, it uses thymine.