Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

7. DNA and Chromosome Structure

DNA Structure

Genetics

7. DNA and Chromosome Structure

DNA Structure

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2:14 minutes

Problem 16a

Textbook Question

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

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.

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.

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.