Which mutations cause a frameshift?
Nonsense and deletion
Missense and insertion
Missense and nonsense
Deletion and insertion
The Correct Answer is D
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.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. Breakdown of molecules to release energy: Catabolism involves the enzymatic breakdown of complex molecules such as carbohydrates, lipids, and proteins into simpler molecules like sugars, fatty acids, and amino acids. This process releases energy, which is captured in the form of ATP to fuel cellular activities, making it a fundamental part of metabolism.
B. Building molecules: The synthesis of complex molecules from simpler ones is called anabolism, not catabolism. Anabolic processes, such as protein synthesis or glycogen formation, require energy input rather than releasing energy.
C. DNA replication: DNA replication is a specific cellular process that duplicates genetic material for cell division. While it is essential for cell survival, it is not a catabolic process, as it does not involve the breakdown of molecules for energy production.
Correct Answer is A
Explanation
The presence of organic matter, such as saliva, pus, blood, or feces, can interfere with the effectiveness of disinfectants. Organic materials can physically shield microorganisms from contact with the disinfectant, reducing its ability to reach and inactivate pathogens. Additionally, some organic compounds can chemically react with the disinfectant, neutralizing its antimicrobial activity. For example, sodium hypochlorite (bleach) can be inactivated by blood or protein-rich substances. Proper pre-cleaning of surfaces to remove organic matter is essential before disinfection to ensure that the disinfectant works effectively and reliably eliminates harmful microorganisms.
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