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Ch. 7 - DNA Structure and Replication
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
All textbooksSanders 3rd EditionCh. 7 - DNA Structure and ReplicationProblem 16b
Chapter 7, Problem 16b

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

Verified step by step guidance
1
Understand Chargaff's rules: 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 is because A pairs with T and G pairs with C.
Express Chargaff's rules mathematically: A = T and G = C. Therefore, the total percentage of purines (A + G) equals the total percentage of pyrimidines (T + C).
Analyze the given equation: The equation (A + T)/(G + C) = 1.0 suggests that the sum of adenine and thymine is equal to the sum of guanine and cytosine in double-stranded DNA.
Consider the implications of Chargaff's rules: While A = T and G = C individually, the ratio (A + T)/(G + C) depends on the specific composition of the DNA and is not necessarily equal to 1.0. The ratio varies depending on the organism's genome.
Conclude the evaluation: Based on Chargaff's rules and the variability of nucleotide composition across different organisms, the equation (A + T)/(G + C) = 1.0 is not universally true for all double-stranded DNA.

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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 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 the percentages of A and T, as well as G and C, are complementary, leading to the conclusion that (A + T) should equal (G + C) in a given DNA sample.
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Base Pairing

Base pairing refers to the specific hydrogen bonding between nucleotides in DNA, where adenine pairs with thymine (A-T) and guanine pairs with cytosine (G-C). This pairing is crucial for the stability of the DNA double helix and ensures accurate replication and transcription of genetic information.
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Nucleotide Composition

The nucleotide composition of DNA refers to the relative amounts of the four nucleotides (A, T, G, C) present in a DNA molecule. Understanding the composition is essential for analyzing genetic sequences and can provide insights into evolutionary relationships and species identification.
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Related Practice
Textbook Question

Bacterial DNA polymerase I and DNA polymerase III perform different functions during DNA replication.

If a strain of E. coli acquired a mutation that inactivated DNA polymerase III function, would the cell be able to replicate its DNA? Why or why not?

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Textbook Question

Diagram a replication fork in bacterial DNA and label the following structures or molecules.

a. DNA pol III

b. Helicase

c. RNA primer

d. Origin of replication

e. leading strand (label its polarity)

f. DNA pol I

g. Topoisomerase

h. SSB protein

i. Lagging strand (label its polarity)

j. Primase

k. Okazaki fragment

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Textbook Question

Which of the following equations are true for the percentages of nucleotides in double-stranded DNA?

(A+G)/(C+T)=1.0

480
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Textbook Question

Which of the following equations are true for the percentages of nucleotides in double-stranded DNA?

(A)/(T)=(G)/(C)

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Textbook Question

Which of the following equations are true for the percentages of nucleotides in double-stranded DNA?

(A)/(C)=(G)/(T)

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Textbook Question

Which of the following equations are true for the percentages of nucleotides in double-stranded DNA?

(A)/(G)=(T)(C)

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