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Chapter 14: Problem 8

What is a purine? a. a double ring structure with a six-membered ring fused to a five-membered ring b. a single six-membered ring c. a six-membered ring d. three phosphates covalently bonded by phosphodiester bonds

Short Answer

Expert verified
Option (a) describes a purine.

Step by step solution

01

- Understanding Ring Structures

Purines and pyrimidines are the two types of nitrogenous bases in nucleic acids, distinguished by their ring structures.
02

- Identifying Purine Structure

Purines are composed of a double ring structure: one six-membered ring fused to a five-membered ring. This sets them apart from pyrimidines, which have only a single six-membered ring.
03

- Analyzing the Answer Choices

Option (a) describes a double ring structure with a six-membered ring fused to a five-membered ring, which matches the definition of a purine. The other options do not describe purines correctly.
04

- Conclusion

Thus, based on our analysis, the correct answer is option (a).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

nitrogenous bases
Nitrogenous bases are essential components of nucleic acids, such as DNA and RNA. These bases fall into two categories: purines and pyrimidines.
The primary function of nitrogenous bases is to store and transfer genetic information. They do this by pairing with each other to form the double helix structure of DNA.
When looking at nitrogenous bases, it's crucial to understand that they each have specific pairing rules. In DNA:
  • Adenine (a purine) pairs with Thymine (a pyrimidine)
  • Guanine (a purine) pairs with Cytosine (a pyrimidine)

In RNA, Thymine is replaced by Uracil as a pyrimidine, which pairs with Adenine. This precise pairing is what allows genetic information to be copied and transmitted accurately.
nucleic acids
Nucleic acids are large biomolecules essential for all known forms of life. They are composed of monomers called nucleotides.
Each nucleotide contains three components: a sugar molecule, a phosphate group, and a nitrogenous base. The sequence of these nucleotides forms the genetic code.
There are two main types of nucleic acids: DNA and RNA.
  • DNA (deoxyribonucleic acid) serves as the long-term storage of genetic information. Its double-stranded structure forms the iconic double helix.
  • RNA (ribonucleic acid) is usually single-stranded and plays various roles in expressing and translating genetic information stored in DNA.

Nucleic acids are crucial in various biological processes including transcription, translation, and replication. Their unique structures allow for the encoding, transmission, and expression of genetic information contained within a cell.
purines and pyrimidines
Purines and pyrimidines are the two main categories of nitrogenous bases found in nucleic acids. Each type has a distinct structure and specific pairing rules.
  • Purines: These include Adenine and Guanine. They are characterized by a double ring structure: one six-membered ring fused to a five-membered ring.
  • Pyrimidines: These include Cytosine, Thymine (in DNA), and Uracil (in RNA). They have a single six-membered ring structure.

The difference in ring structure between purines and pyrimidines is crucial for the formation of stable DNA and RNA molecules. The consistent pairing between a purine and a pyrimidine (A-T or A-U, and G-C) helps maintain the uniform width of the DNA double helix.
This structural difference also aids in various biological functions, such as enzyme recognition and the accurate transmission of genetic information.

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Most popular questions from this chapter

Discuss the contributions of Francis Crick, James Watson, and Rosalind Franklin to the discovery of the structure of DNA. a. Rosalind Franklin used X-ray diffraction methods to demonstrate the helical nature of DNA, while Watson and Crick formulated the double stranded structural model of DNA. b. Rosalind Franklin, Watson and Crick first employed the technique of X-ray diffraction to understand the storage of DNA. Since it did not work out, Watson and Crick then ran experiments to ascertain the DNA structure. c. Rosalind Franklin, Watson and Crick used X-ray diffraction methods to demonstrate the helical nature of DNA, while Rosalind Franklin formulated the double stranded structural model of DNA. d. Watson and Crick used X-ray diffraction methods to demonstrate the helical nature of DNA, while Rosalind Franklin formulated the double stranded structural model of DNA.

Which set of results was found in the Meselson and Stahl鈥檚 experiments? a. The original chromosome was kept intact and a duplicate was made. b. The original chromosome was split and half went to each duplicate. c. The original chromosome was mixed with new material and each duplicate strand contained both old and new. d. The original chromosome was used as a template for two new chromosomes and discarded.

What is bacterial transformation? a. The transformation of a bacterium occurs during replication. b. It is the transformation of a bacterium into a pathogenic form. c. Transformation of bacteria involves changes in its chromosome. d. Transformation is a process in which external DNA is taken up by a cell, thereby changing morphology and physiology.

In which direction does DNA replication take place? a. 5鈥� to 3鈥� b. 3鈥� to 5鈥� c. 5鈥� d. 3鈥�

Discuss the effects of point mutations on a DNA strand. a. Mutations can cause a single change in an amino acid. A nonsense mutation can stop the replication or reading of that strand. Insertion or deletion mutations can cause a frame shift. This can result in non-functional proteins. b. Mutations can cause a single change in amino acid. A missense mutation can stop the replication or reading of that strand. Insertion or deletion mutations can cause a frame shift. This can result in non-functional proteins. c. Mutations can cause a single change in amino acid. A nonsense mutation can stop the replication or reading of that strand. Substitution mutations can cause a frame shift. This can result in non-functional proteins. d. Mutations can cause a single change in amino acid. A nonsense mutation can stop the replication or reading of that strand. Insertion or deletion mutations can cause a frame shift. This can result in functional proteins.
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