Textbook Question
Cyclohexane, C6H12, is an important starting material used in the industrial synthesis of nylon. Each carbon has four covalent bonds, two to hydrogen and two to other carbons. Draw the structural formula of cyclohexane.
Ch.23 - Organic and Biological Chemistry
Chapter 23, Problem 131
The DNA from sea urchins contains about 32% A and about 18% G. What percentages of T and C would you expect in sea urchin DNA? Explain.
Verified step by step guidance1
Step 1: Understand the base pairing rules in DNA. Adenine (A) pairs with Thymine (T), and Guanine (G) pairs with Cytosine (C). This means the percentage of A should equal the percentage of T, and the percentage of G should equal the percentage of C.
Step 2: Given that the DNA contains 32% A, use the base pairing rule to determine the percentage of T. Since A pairs with T, the percentage of T should also be 32%.
Step 3: Calculate the total percentage of A and T in the DNA. Since both A and T are 32%, add these percentages together: 32% + 32% = 64%.
Step 4: Determine the remaining percentage of the DNA that is composed of G and C. Since the total percentage of all bases in DNA must equal 100%, subtract the percentage of A and T from 100%: 100% - 64% = 36%.
Step 5: Use the base pairing rule to find the percentage of C. Given that G is 18%, and G pairs with C, the percentage of C should also be 18%. Verify that the sum of G and C equals the remaining percentage: 18% + 18% = 36%.
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Chargaff's Rules
Chargaff's Rules state that in a double-stranded DNA molecule, the amount of adenine (A) is equal to thymine (T), and the amount of guanine (G) is equal to cytosine (C). This means that the percentages of A and T, as well as G and C, must be equal in a given DNA sample, which is crucial for understanding the base pairing in DNA.
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Solubility Rules
Base Pairing in DNA
Base pairing in DNA refers to the specific pairing of nitrogenous bases: adenine pairs with thymine, and guanine pairs with cytosine. This complementary nature of base pairing is fundamental to the structure of DNA and is essential for processes such as DNA replication and transcription.
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Percentage Composition of DNA Bases
The percentage composition of DNA bases provides insight into the relative amounts of each base present in a DNA sample. By knowing the percentages of A and G, one can calculate the percentages of T and C using Chargaff's Rules, allowing for a complete understanding of the DNA's base composition.
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