Textbook Question
The drugs ddC and AZT are used to treat AIDS.
Based on their chemical structures, what is their mode of action?
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Ch. 7 - Microbial Genetics
Bauman6th EditionMicrobiology with Diseases by TaxonomyISBN: 9780134832302
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Table of contents
- Ch. 1 - A Brief History of Microbiology31
- Ch. 2 - The Chemistry of Microbiology28
- Ch. 3 - Cell Structure and Function39
- Ch. 4 - Microscopy, Staining, and Classification25
- Ch. 5 - Microbial Metabolism51
- Ch. 6 - Microbial Nutrition and Growth37
- Ch. 7 - Microbial Genetics51
- Ch. 8 - Recombinant DNA Technology21
- Ch. 9 - Controlling Microbial Growth in the Environment36
- Ch. 10 - Controlling Microbial Growth in the Body: Antimicrobial Drugs21
- Ch. 11 - Characterizing and Classifying Prokaryotes29
- Ch. 12 - Characterizing and Classifying Eukaryotes34
- Ch. 13 - Characterizing and Classifying Viruses, Viroids, and Prions23
- Ch. 14 - Infection, Infectious Diseases, and Epidemiology35
- Ch. 15 - Innate Immunity34
- Ch. 16 - Adaptive Immunity21
- Ch. 17 - Immunization and Immune Testing29
- Ch. 18 - Immune Disorders22
- Ch. 19 - Pathogenic Gram-Positive Bacteria25
- Ch. 20 - Pathogenic Gram-Negative Cocci and Bacilli28
- Ch. 21 - Rickettsias, Chlamydias, Spirochetes, and Vibrios25
- Ch. 22 - Pathogenic Fungi47
- Ch. 23 - Parasitic Protozoa, Helminths, and Arthropod Vectors44
- Ch. 24 - Pathogenic DNA Viruses23
- Ch. 25 - Pathogenic RNA Viruses30
- Ch. 26 - Applied and Industrial Microbiology29
- Ch. 27 - Microbial Ecology and Microbiomes22
Bauman6th EditionMicrobiology with Diseases by TaxonomyISBN: 9780134832302Not the one you use?Change textbook
Chapter 7, Problem 3
A plasmid is __________ .
a. a molecule of RNA found in bacterial cells
b. distinguished from a chromosome by being circular
c. a structure in bacterial cells formed from plasma membrane
d. extrachromosomal DNA
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Understand the definition of a plasmid: A plasmid is a small, circular DNA molecule that exists independently of the chromosomal DNA in bacterial cells.
Recall that plasmids are not RNA molecules, so option (a) can be ruled out because plasmids are DNA, not RNA.
Consider the shape of plasmids: while many plasmids are circular, bacterial chromosomes can also be circular, so being circular alone does not distinguish plasmids from chromosomes, making option (b) incomplete or misleading.
Recognize that plasmids are not structures formed from the plasma membrane, so option (c) is incorrect.
Identify that plasmids are extrachromosomal DNA, meaning they exist outside the main bacterial chromosome, which matches option (d).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Plasmid Definition
A plasmid is a small, circular DNA molecule found in bacterial cells that exists independently of the chromosomal DNA. It carries genes that can provide advantageous traits, such as antibiotic resistance, and can replicate autonomously.
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Chromosomal DNA vs. Extrachromosomal DNA
Chromosomal DNA contains the essential genetic information for the cell's survival, while extrachromosomal DNA, like plasmids, exists outside the chromosome and often carries non-essential but beneficial genes. Plasmids are a common form of extrachromosomal DNA in bacteria.
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Structure and Composition of Plasmids
Plasmids are typically circular double-stranded DNA molecules, distinct from linear chromosomal DNA. They are not formed from the plasma membrane or RNA, but are separate genetic elements that can be transferred between bacteria.
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Related Practice
Textbook Question
Insertions and deletions in the genetic code are also called ___________ mutations.
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Textbook Question
Polypeptide synthesis requires large amounts of energy. How do cells regulate synthesis to conserve energy? Describe one specific example.
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Textbook Question
Compare and contrast introns and exons.
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Textbook Question
Three effects of point mutations are ___________ , ___________ , and ____________ .
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Textbook Question
Which of the following forms ionic bonds with eukaryotic DNA and stabilizes it?
a. Chromatin
b. Bacteriocin
c. Histone
d. Nucleoid
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