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

Verified step by step guidance

1. Understand the structure of double-stranded DNA: DNA is composed of four nucleotide bases - adenine (A), thymine (T), guanine (G), and cytosine (C). In double-stranded DNA, base pairing occurs such that A pairs with T and G pairs with C.
2. Recall Chargaff's rules: Chargaff's rules state that in double-stranded DNA, the amount of adenine (A) is equal to the amount of thymine (T), and the amount of guanine (G) is equal to the amount of cytosine (C). This can be expressed as A = T and G = C.
3. Analyze the given equation: The equation provided is (A)/(T) = (G)/(C). Using Chargaff's rules, substitute A = T and G = C into the equation. This simplifies the equation to 1 = 1, which is true.
4. Interpret the equation: The equation (A)/(T) = (G)/(C) essentially reflects the proportionality of nucleotide pairing in double-stranded DNA. Since A pairs with T and G pairs with C, the ratios of A to T and G to C are both equal to 1.
5. Conclude the validity of the equation: Based on Chargaff's rules and the structure of double-stranded DNA, the equation (A)/(T) = (G)/(C) is true for the percentages of nucleotides in double-stranded DNA.

Key Concepts

Chargaff's Rules

Chargaff's Rules state that in double-stranded DNA, the amount of adenine (A) is equal to thymine (T), and the amount of guanine (G) is equal to cytosine (C). This means that A pairs with T and G pairs with C, leading to the conclusion that the ratios of these nucleotides are consistent across different organisms.

Base Pairing

Base pairing refers to the specific hydrogen bonding between nucleotide bases in DNA. Adenine pairs with thymine through two hydrogen bonds, while guanine pairs with cytosine through three hydrogen bonds. This complementary pairing is crucial for the stability of the DNA double helix and ensures accurate DNA replication.

Double-Stranded DNA Structure

Double-stranded DNA consists of two strands that run in opposite directions, forming a double helix. Each strand is composed of a sugar-phosphate backbone and nitrogenous bases. The antiparallel nature of the strands and the specific base pairing are essential for the integrity and function of genetic material, influencing processes like transcription and replication.