The minimum number of microbes needed to cause infection is:
Infectious dose
Mutation rate
Growth rate
The Correct Answer is A
A. Infectious dose: The infectious dose (ID) refers to the minimum number of microorganisms required to establish an infection in a host. Different pathogens have varying IDs depending on their virulence, host susceptibility, and route of entry. A lower infectious dose indicates higher virulence, while a higher dose may be required for less virulent organisms.
B. Mutation rate: Mutation rate describes how frequently changes occur in the genetic material of an organism. While mutations can affect virulence, antibiotic resistance, or adaptability, mutation rate does not define the number of microbes required to initiate infection.
C. Growth rate: Growth rate refers to how quickly microorganisms replicate under optimal conditions. Although rapid growth can contribute to the severity of an infection, it does not determine the minimum number of organisms necessary to cause disease. The infectious dose specifically quantifies that threshold.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
Both facilitated diffusion and active transport require carrier proteins to move substances across the plasma membrane, but the mechanisms differ. Facilitated diffusion uses carrier or channel proteins to transport molecules down their concentration gradient without energy expenditure. In contrast, active transport also uses carrier proteins but moves substances against their concentration gradient, requiring energy input, usually from ATP hydrolysis. These proteins provide specificity for particular molecules and enable transport that cannot occur through simple diffusion, ensuring that cells can regulate nutrient uptake, ion balance, and waste removal efficiently.
50/106
Correct Answer is D
Explanation
A. Nonsense and deletion: A nonsense mutation occurs when a codon that normally codes for an amino acid is changed into a stop codon, causing premature termination of protein synthesis. Although deletions can cause frameshifts, nonsense mutations themselves do not alter the reading frame. Therefore, this combination does not consistently produce frameshift mutations.
B. Missense and insertion: A missense mutation results from a single nucleotide substitution that changes one amino acid in the protein sequence. This alters protein structure but does not shift the reading frame. While insertions can cause frameshifts, the combination listed does not accurately represent the mechanisms responsible for frameshift mutations.
C. Missense and nonsense: Both missense and nonsense mutations are types of point mutations caused by single base substitutions. These mutations affect the identity of a codon or create a premature stop codon but do not alter the grouping of codons into triplets. As a result, they do not shift the reading frame of the genetic code.
D. Deletion and insertion: Frameshift mutations occur when nucleotides are inserted into or deleted from the DNA sequence in numbers not divisible by three. Because the genetic code is read in triplets (codons), such changes shift the reading frame downstream of the mutation. This alters all subsequent codons and often results in a drastically altered or nonfunctional protein.
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