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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 16a
Chapter 7, Problem 16a

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.
Express the base-pairing rules mathematically: A = T and G = C. This is a fundamental property of DNA structure based on Chargaff's rules.
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).
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.
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.

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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) 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.
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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.
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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.
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Related Practice
Textbook Question

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

If mutation inactivated DNA polymerase I in a strain of E. coli, would the cell be able to replicate its DNA? If so, what kind of abnormalities would you expect to find in the cell?

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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?

915
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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+T)/(G+C)=1.0

471
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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)

411
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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)

499
views