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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1:17 minutes

Problem 30c

Textbook Question

Consider the drawing of a dinucleotide below.
Suppose that the molecule was cleaved with the enzyme spleen phosphodiesterase, which breaks the covalent bond connecting the phosphate to C-5'. After cleavage, to which nucleoside is the phosphate now attached (A or T)?

Verified step by step guidance

Understand the structure of a dinucleotide: A dinucleotide consists of two nucleotides connected by a phosphodiester bond. Each nucleotide is made up of a sugar (deoxyribose in DNA), a phosphate group, and a nitrogenous base (Adenine (A) or Thymine (T) in this case).

Identify the role of spleen phosphodiesterase: This enzyme specifically cleaves the phosphodiester bond between the phosphate group and the 5' carbon of the sugar in the nucleotide. This means the phosphate group will no longer be attached to the 5' carbon of one nucleotide.

Determine the result of cleavage: After the cleavage, the phosphate group will remain attached to the 3' carbon of the sugar in the adjacent nucleotide. This is because the phosphodiester bond connects the 5' carbon of one nucleotide to the 3' carbon of the next nucleotide.

Analyze the dinucleotide structure: In the given dinucleotide, identify which nucleotide (A or T) has its phosphate group originally attached to the 5' carbon. After cleavage, the phosphate will transfer to the 3' carbon of the adjacent nucleotide.

Conclude the attachment: Based on the cleavage mechanism, determine whether the phosphate group is now attached to the nucleoside containing Adenine (A) or Thymine (T). This depends on the orientation of the dinucleotide and the position of the cleavage.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Nucleotides and Nucleosides

Nucleotides are the building blocks of nucleic acids, consisting of a phosphate group, a sugar (ribose or deoxyribose), and a nitrogenous base (adenine, thymine, cytosine, or guanine). Nucleosides are similar but lack the phosphate group, comprising only the sugar and the nitrogenous base. Understanding the difference between these two is crucial for analyzing the effects of enzymatic cleavage on nucleic acid structure.

Phosphodiester Bonds

Phosphodiester bonds are covalent linkages that connect the phosphate group of one nucleotide to the hydroxyl group on the sugar of another nucleotide, forming the backbone of DNA and RNA. The cleavage of these bonds by enzymes like spleen phosphodiesterase alters the structure of nucleic acids, impacting their function and stability. Recognizing how these bonds are formed and broken is essential for understanding the question.

Enzymatic Cleavage

Enzymatic cleavage refers to the process by which enzymes break specific chemical bonds in molecules. In this case, spleen phosphodiesterase cleaves the bond between the phosphate group and the C-5' carbon of the sugar in a nucleotide. This action determines the attachment of the phosphate group to either adenine (A) or thymine (T), which is critical for answering the question regarding the resulting nucleoside.

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Textbook Question

A genetics student was asked to draw the chemical structure of an adenine- and thymine-containing dinucleotide derived from DNA. The answer is shown here:

The student made more than six major errors. One of them is circled, numbered 1, and explained. Find five others. Circle them, number them 2 through 6, and briefly explain each in the manner of the example given.

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Textbook Question

One of the most common spontaneous lesions that occurs in DNA under physiological conditions is the hydrolysis of the amino group of cytosine, converting the cytosine to uracil. What would be the effect on DNA structure of a uracil group replacing cytosine?

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Textbook Question

In some organisms, cytosine is methylated at carbon 5 of the pyrimidine ring after it is incorporated into DNA. If a 5-methyl cytosine molecule is then hydrolyzed, what base will be generated?

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Textbook Question

Consider the drawing of a dinucleotide below.

Is the arrow closest to the 5' or the 3' end?

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Textbook Question

Consider the drawing of a dinucleotide below.

Is it DNA or RNA?

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