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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Multiple Choice

Which of the following statements correctly describes purines and pyrimidines in DNA molecules?

Purines are double-ringed bases (adenine and guanine), while pyrimidines are single-ringed bases (cytosine and thymine).

Purines are single-ringed bases (cytosine and thymine), while pyrimidines are double-ringed bases (adenine and guanine).

Purines and pyrimidines are both found only in RNA, not in DNA.

Both purines and pyrimidines are double-ringed structures in DNA.

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Verified step by step guidance

Step 1: Understand the basic structure of nitrogenous bases in nucleic acids. There are two categories: purines and pyrimidines, which differ in their ring structures.

Step 2: Recall that purines have a double-ring structure composed of a six-membered and a five-membered nitrogen-containing ring fused together.

Step 3: Recall that pyrimidines have a single six-membered nitrogen-containing ring.

Step 4: Identify which bases belong to each category in DNA: adenine (A) and guanine (G) are purines, while cytosine (C) and thymine (T) are pyrimidines.

Step 5: Use this information to evaluate the statements and determine that the correct description is that purines are double-ringed bases (adenine and guanine), and pyrimidines are single-ringed bases (cytosine and thymine).