Textbook Question
Which of the following equalities is not true for double-stranded DNA?
(G+C)=(A+T)
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Ch. 7 - DNA Structure and Replication
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172
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Table of contents
- Ch. 1 - The Molecular Basis of Heredity, Variation, and Evolution64
- Ch. 2 - Transmission Genetics144
- Ch. 3 - Cell Division and Chromosome Heredity81
- Ch. 4 - Gene Interaction87
- Ch. 5 - Genetic Linkage and Mapping in Eukaryotes103
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages73
- Ch. 7 - DNA Structure and Replication71
- Ch. 8 - Molecular Biology of Transcription and RNA Processing79
- Ch. 9 - The Molecular Biology of Translation110
- Ch. 10 - Eukaryotic Chromosome Abnormalities and Molecular Organization100
- Ch. 11 - Gene Mutation, DNA Repair, and Homologous Recombination86
- Ch. 12 - Regulation of Gene Expression in Bacteria and Bacteriophage90
- Ch. 13 - Regulation of Gene Expression in Eukaryotes38
- Ch. 14 - Analysis of Gene Function via Forward Genetics and Reverse Genetics72
- Ch. 15 - Recombinant DNA Technology and Its Applications69
- Ch. 16 - Genomics: Genetics from a Whole-Genome Perspective49
- Ch. 17 - Organelle Inheritance and the Evolution of Organelle Genomes27
- Ch. 18 - Developmental Genetics43
- Ch. 19 - Genetic Analysis of Quantitative Traits66
- Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels105
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
Chapter 7, Problem 19
Two viral genomes are sequenced, and the following percentages of nucleotides are identified:
Genome 1: A=28%, C=22%,G=28%,T=22%
Genome 2: A=22%, C=28%,G=28%,T=22%
Are the DNA molecules in each genome single-stranded or double-stranded?
Verified step by step guidance1
Analyze the nucleotide composition of each genome. In double-stranded DNA, the base pairing rule (Chargaff's rule) states that the percentage of adenine (A) equals the percentage of thymine (T), and the percentage of cytosine (C) equals the percentage of guanine (G). This is because A pairs with T, and C pairs with G in double-stranded DNA.
For Genome 1, compare the percentages of A and T, and C and G. Here, A = 28% and T = 22%, which are not equal. Similarly, C = 22% and G = 28%, which are also not equal. This suggests that Genome 1 does not follow Chargaff's rule and is likely single-stranded.
For Genome 2, compare the percentages of A and T, and C and G. Here, A = 22% and T = 22%, which are equal. Similarly, C = 28% and G = 28%, which are also equal. This indicates that Genome 2 follows Chargaff's rule and is likely double-stranded.
Summarize the findings: Genome 1 is single-stranded because it does not follow Chargaff's rule, while Genome 2 is double-stranded because it adheres to Chargaff's rule.
Conclude by emphasizing the importance of Chargaff's rule in determining whether a DNA molecule is single-stranded or double-stranded, based on the nucleotide composition.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Base Pairing Rules
In double-stranded DNA, nucleotides pair specifically: adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). This complementary base pairing is crucial for the stability and replication of DNA. In single-stranded DNA, these pairing rules do not apply, as there is no complementary strand to bind with.
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03:49
Base Distortions
Nucleotide Composition
The composition of nucleotides in a genome can provide insights into its structure. In double-stranded DNA, the percentages of A and T should be roughly equal, as should the percentages of C and G, due to base pairing. In contrast, single-stranded DNA does not exhibit this complementary relationship, leading to potentially unequal nucleotide ratios.
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06:51Human Genome Composition
Genome Structure
The overall structure of a genome influences its function and stability. Double-stranded DNA forms a helical structure that is more stable and less prone to degradation than single-stranded DNA. Understanding whether a genome is single or double-stranded is essential for interpreting its biological properties and behavior during processes like replication and transcription.
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Related Practice
Textbook Question
Which of the following equalities is not true for double-stranded DNA?
(G+A)=(C+T)
468
views
Textbook Question
List the order in which the following proteins and enzymes are active in E. coli DNA replication: DNA pol I, SSB, ligase, helicase, DNA pol III, and primase.
471
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Textbook Question
Matthew Meselson and Franklin Stahl demonstrated that DNA replication is semiconservative in bacteria. Briefly outline their experiment and its results for two DNA replication cycles, and identify how the alternative models of DNA replication were excluded by the data.
723
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Textbook Question
Raymond Rodriguez and colleagues demonstrated conclusively that DNA replication in E. coli is bidirectional. Explain why locating the origin of replication on one side of the circular chromosomes and the terminus of replication on the opposite side of the chromosome supported this conclusion.
437
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Textbook Question
Joel Huberman and Arthur Riggs used pulse–chase labeling to examine the replication of DNA in mammalian cells. Briefly describe the Huberman–Riggs experiment, and identify how the results exclude a unidirectional model of DNA replication.
1050
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