Which of the following equations are true for the percentages of nucleotides in double-stranded DNA?
(A+G)/(C+T)=1.0

Verified step by step guidance

1. Understand the context: In double-stranded DNA, the base-pairing rules state that adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C). This means the amount of A equals T, and the amount of G equals C.
2. Express the base-pairing rules mathematically: A = T and G = C. This is a fundamental property of DNA structure based on Chargaff's rules.
3. Combine the base-pairing rules to analyze the given equation: The total amount of purines (A + G) will equal the total amount of pyrimidines (C + T) in double-stranded DNA. Therefore, (A + G) = (C + T).
4. Simplify the given equation: Divide both sides of the equation (A + G) = (C + T) by (C + T) to confirm that (A + G)/(C + T) = 1.0.
5. Conclude that the equation is true: Based on the mathematical derivation and the base-pairing rules, the equation (A + G)/(C + T) = 1.0 is valid for double-stranded DNA.

Key Concepts

Chargaff's Rules

Chargaff's Rules state that in double-stranded DNA, the amount of adenine (A) equals thymine (T), and the amount of guanine (G) equals cytosine (C). This means that A + G will equal C + T, leading to the conclusion that the ratio of purines (A and G) to pyrimidines (C and T) is always 1:1 in a double-stranded DNA molecule.

Nucleotide Composition

Nucleotides are the building blocks of DNA, consisting of a sugar, a phosphate group, and a nitrogenous base. In double-stranded DNA, the composition of these nucleotides is crucial for understanding the structure and function of DNA, as the specific pairing of bases (A with T and G with C) ensures the stability and integrity of the genetic information.

Base Pairing and Stability

Base pairing refers to the specific hydrogen bonding between nitrogenous bases in DNA, where adenine pairs with thymine and guanine pairs with cytosine. This complementary pairing not only stabilizes the double helix structure of DNA but also plays a critical role in DNA replication and transcription, ensuring accurate genetic information transfer.