Question

Nucleic Acid Identity Explain how RNA nucleotides differ from DNA nucleotides.

Short answer

RNA nucleotides use ribose sugar and uracil base, whereas DNA nucleotides use deoxyribose sugar and thymine base.

Step-by-step solution

Recognize the components of nucleotides

Both RNA and DNA nucleotides consist of three components: a phosphate group, a five-carbon sugar, and a nitrogenous base. These components are essential for forming the backbone and the genetic code.

Identify the sugar differences

In DNA, the sugar component is deoxyribose, which lacks an oxygen atom on the 2' carbon - this is where it gets its name ('deoxy' = 'lacking oxygen'). RNA, on the other hand, contains ribose, which has a hydroxyl group (-OH) attached to the 2' carbon, making it chemically more reactive than deoxyribose.

Examine the nitrogenous base differences

RNA and DNA share three of the four nitrogenous bases: adenine (A), guanine (G), and cytosine (C). The difference lies in the fourth base: DNA uses thymine (T), while RNA uses uracil (U) instead. This change affects the pairing and structure of the nucleic acid.

Key concepts

RNA Nucleotides

RNA nucleotides are the building blocks of RNA molecules, essential for various functions including protein synthesis. Each RNA nucleotide includes three main components:

• A nitrogenous base: adenine (A), guanine (G), cytosine (C), or uracil (U).
• A ribose sugar: a five-carbon sugar with a hydroxyl group (-OH) at the 2' carbon.
• A phosphate group: which forms the backbone of the RNA strand.

A unique characteristic of RNA is the presence of uracil, which replaces the thymine found in DNA. This means that in RNA, uracil pairs with adenine during the formation of base pairs. RNA's single-stranded nature and its ribose sugar make it more flexible and chemically versatile, allowing it to take on different shapes necessary for its functions.

DNA Nucleotides

DNA nucleotides are the basic units of DNA, carrying the genetic blueprint for organisms. Each DNA nucleotide is composed of:

• A nitrogenous base: adenine (A), guanine (G), cytosine (C), or thymine (T).
• A deoxyribose sugar: a five-carbon sugar that lacks an oxygen atom at the 2' carbon.
• A phosphate group: which connects nucleotides together to form DNA strands.

In contrast to RNA, DNA is double-stranded and features thymine instead of uracil. Thymine pairs with adenine via two hydrogen bonds, contributing to the stability of DNA's double helix structure. The stability is crucial for DNA's role in long-term information storage within cells.

Sugar Differences

One of the key differences between RNA and DNA nucleotides is the sugar component. This difference significantly impacts the structure and function of these nucleic acids.

• DNA contains deoxyribose sugar. It lacks an oxygen atom on the 2' carbon, hence the name "deoxy". This absence makes DNA more stable and less reactive.
• RNA contains ribose sugar. It features a hydroxyl group (-OH) on the 2' carbon. This presence makes RNA more chemically reactive and allows it to perform various functions besides encoding genetic information, such as catalysis (ribozymes) and regulation (RNA interference).

The structural differences in sugars contribute to the unique roles of RNA and DNA in cells, with DNA acting as the stable keeper of genetic code and RNA adapting to different functional tasks as required.

Nitrogenous Bases

Nitrogenous bases are critical in storing genetic information and facilitating base pairing. Both RNA and DNA include some common bases, however, there is a fundamental difference in one of these bases.

• Adenine (A), guanine (G), and cytosine (C) are present in both RNA and DNA.
• DNA contains thymine (T), while RNA features uracil (U).

In terms of base pairing, thymine in DNA pairs with adenine via two hydrogen bonds. In RNA, uracil serves the same function, forming hydrogen bonds with adenine. This subtle yet significant difference affects the structure and function of the nucleic acids. For example, the replacement of thymine with uracil in RNA makes it less stable than DNA, as the uracil-adenine pairing is slightly weaker. It reflects the transient nature of RNA in the cell's processes.