Question

Which of the following statements regarding differences between DNA and RNA is FALSE? a. In cells, DNA is double-stranded, whereas RNA is single- stranded. b. DNA uses the nitrogenous base thymine; RNA uses uracil. c. The sugar in DNA is deoxyribose; the sugar in RNA is ribose. d. DNA strands replicate in a \(5^{\prime}\) to \(3^{\prime}\) direction, whereas RNA is synthesized in a \(3^{\prime}\) to \(5^{\prime}\) direction.

Short answer

The false statement is d.

Step-by-step solution

Analyze Statement a

In cells, DNA is typically double-stranded, while RNA is usually single-stranded. This statement is true.

Analyze Statement b

DNA uses the nitrogenous base thymine and RNA uses uracil. This statement is true.

Analyze Statement c

The sugar in DNA is deoxyribose, whereas the sugar in RNA is ribose. This statement is true.

Analyze Statement d

DNA strands replicate in a 5' to 3' direction. RNA is also synthesized in a 5' to 3' direction, not in a 3' to 5' direction. This statement is false.

Conclusion

From the analysis, it can be concluded that the false statement is d.

Key concepts

DNA structure

DNA, or deoxyribonucleic acid, is the molecule that carries the genetic instructions used in the growth, development, functioning, and reproduction of all known living organisms. DNA is typically a double-stranded molecule, which means it has two long strands that form a double helix structure. The double helix looks like a twisted ladder. Each 'rung' of the ladder is made up of pairs of nitrogenous bases. These pairs are held together by hydrogen bonds, making the structure both stable and compact.
The backbone of each DNA strand is made of a sugar called deoxyribose, which is connected to phosphate groups. This forms a sugar-phosphate backbone. DNA is also characterized by its replication process, which occurs in a specific direction: from the 5' (five-prime) end to the 3' (three-prime) end.

RNA structure

RNA, or ribonucleic acid, plays multiple roles in the cell, including acting as a messenger that carries instructions from DNA for controlling protein synthesis. RNA is typically single-stranded, unlike the double-stranded structure of DNA. However, RNA can fold into complex three-dimensional shapes due to internal complementary base pairing.
The backbone of RNA is also composed of a sugar and phosphate chain, but the sugar in RNA is ribose, not deoxyribose. Whereas DNA's structure is quite stable, RNA is usually more unstable and prone to degradation. RNA synthesis also follows a directional process similar to DNA replication, moving from the 5' to the 3' end.

Nucleotide bases

Nucleotide bases are the building blocks of nucleic acids like DNA and RNA. In DNA, there are four types of nucleotide bases: adenine (A), thymine (T), cytosine (C), and guanine (G). Adenine pairs with thymine, and cytosine pairs with guanine, forming the rungs of the DNA ladder.
In RNA, the base thymine is replaced by uracil (U). So, in RNA, adenine pairs with uracil, while cytosine still pairs with guanine. These pairs are essential for the processes of transcription and translation in the cell's protein synthesis machinery.

Sugar components in nucleic acids

The sugar component of nucleic acids is crucial for the structure and function of DNA and RNA. In DNA, the sugar is deoxyribose. Deoxyribose is a five-carbon sugar that lacks one oxygen atom, making it more chemically stable and suitable for storing genetic information long-term.
In contrast, RNA contains ribose, which has an additional oxygen atom. This makes RNA more reactive and less stable than DNA. The difference in sugars contributes to the different roles DNA and RNA play in cells. DNA's stability allows it to serve as a long-term store of genetic information, while RNA's structure enables it to perform various functions, including acting as a messenger, a catalyst in some biological reactions, and a component of the ribosome.