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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3:09 minutes

Problem 12

Textbook Question

Adenine may also be named 6-amino purine. How would you name the other four nitrogenous bases, using this alternative system? (O is indicated by 'oxy-,' and CH₃ by 'methyl.')

Verified step by step guidance

Identify the chemical structure of each nitrogenous base: adenine, guanine, cytosine, thymine, and uracil.

For guanine, note that it is a purine with an amino group at position 2 and a keto group at position 6. Thus, it can be named 2-amino-6-oxy purine.

For cytosine, recognize it as a pyrimidine with an amino group at position 4 and a keto group at position 2. Therefore, it can be named 4-amino-2-oxy pyrimidine.

For thymine, observe that it is a pyrimidine with keto groups at positions 2 and 4, and a methyl group at position 5. Hence, it can be named 5-methyl-2,4-dioxy pyrimidine.

For uracil, identify it as a pyrimidine with keto groups at positions 2 and 4. Thus, it can be named 2,4-dioxy pyrimidine.

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Key Concepts

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

Nitrogenous Bases

Nitrogenous bases are organic molecules that contain nitrogen and are fundamental components of nucleotides, which make up DNA and RNA. The primary nitrogenous bases in nucleic acids are adenine (A), thymine (T), cytosine (C), guanine (G), and uracil (U). Understanding their structure and function is essential for grasping genetic coding and the mechanisms of heredity.

Nomenclature of Nitrogenous Bases

The nomenclature of nitrogenous bases can vary based on their chemical structure. For example, adenine is referred to as 6-amino purine due to its amino group at the 6th carbon position in the purine ring. This systematic naming helps in identifying the specific chemical modifications of the bases, which is crucial for understanding their roles in nucleic acids.

Chemical Modifications

Chemical modifications of nitrogenous bases, such as the addition of methyl or oxy groups, can significantly affect their properties and functions. For instance, the presence of a methyl group in thymine distinguishes it from uracil, which lacks this modification. Recognizing these modifications is important for understanding base pairing and the stability of nucleic acids.

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Textbook Question

Consider the sequence 3'-ACGCTACGTC-5'.

What is the double-stranded sequence?

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Textbook Question

Draw the chemical structure of the three components of a nucleotide, and then link the three together. What atoms are removed from the structures when the linkages are formed?

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Textbook Question

How are the carbon and nitrogen atoms of the sugars, purines, and pyrimidines numbered?

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Textbook Question

Human adult hemoglobin is a tetramer containing two alpha (α) and two beta (β) polypeptide chains. The α gene cluster on chromosome 16 and the β gene cluster on chromosome 11 share amino acid similarities such that 61 of the amino acids of the α-globin polypeptide (141 amino acids long) are shared in identical sequence with the β-globin polypeptide (146 amino acids long). How might one explain the existence of two polypeptides with partially shared function and structure on two different chromosomes?

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Textbook Question

Draw the chemical structure of a dinucleotide composed of A and G. Opposite this structure, draw the dinucleotide composed of T and C in an antiparallel (or upside-down) fashion. Form the possible hydrogen bonds.

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Textbook Question

Which of the following equations are true for the percentages of nucleotides in double-stranded DNA?

(A)/(G)=(T)(C)

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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)

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