The transfer of DNA fragments from a dead cell to a live, competent recipient cell that results in a changed recipient cell is
conjugation.
mitosis.
transmission.
transformation.
transduction.
The Correct Answer is D
A. conjugation: Conjugation is the transfer of genetic material between bacterial cells through direct cell-to-cell contact, usually via a pilus. It requires live donor and recipient cells and is not mediated by DNA from a dead cell.
B. mitosis: Mitosis is the process of eukaryotic cell division, resulting in two genetically identical daughter cells. It does not involve horizontal gene transfer or the uptake of DNA from other cells.
C. transmission: Transmission is a general term for the spread of organisms or genetic material but does not specifically describe the process in which a dead cell’s DNA is incorporated into a living recipient cell.
D. transformation: Transformation is the process by which a competent bacterial cell takes up DNA fragments from a dead or lysed cell in its environment. This exogenous DNA can be incorporated into the recipient’s genome, resulting in a genetically altered cell, a mechanism first described in Streptococcus pneumoniae by Griffith.
E. transduction: Transduction is the transfer of bacterial DNA from one cell to another via bacteriophages (viruses that infect bacteria). Unlike transformation, it requires a viral vector rather than direct uptake of free DNA from a dead cell.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. Secreted protein toxins: Exotoxins are proteins actively secreted by certain bacteria into their surrounding environment. They are highly potent and can cause specific damage to host cells or tissues, such as neurotoxins (Clostridium tetani), enterotoxins (Vibrio cholerae), or cytotoxins (Corynebacterium diphtheriae). Being protein in nature, they are often heat-labile and can stimulate strong immune responses, making them targets for toxoid vaccines.
B. Lipid toxins: Lipid-based toxins, such as lipopolysaccharides (LPS), are characteristic of endotoxins, not exotoxins. Endotoxins are part of the outer membrane of Gram-negative bacteria and are released mainly when the bacterial cell dies, producing systemic effects like fever and inflammation rather than specific cellular targeting.
C. DNA toxins: There are no naturally occurring bacterial toxins that are composed of DNA. While bacterial DNA can be transferred via plasmids or phages to spread virulence factors, DNA itself does not function as a secreted toxin causing direct cellular damage.
Correct Answer is C
Explanation
A. Glycolysis: Glycolysis produces a small amount of ATP directly through substrate-level phosphorylation, yielding 2 ATP molecules per glucose molecule. While it initiates the breakdown of glucose to pyruvate, the majority of energy is not generated at this stage.
B. All phases produce the same number of ATP molecules: ATP production is not uniform across the phases of cellular respiration. Each phase contributes differently, with oxidative phosphorylation generating the largest share of ATP, making this statement incorrect.
C. Oxidative phosphorylation (Electron Transport Chain): The electron transport chain and chemiosmosis in oxidative phosphorylation produce the majority of ATP during cellular respiration, typically yielding 34 ATP per glucose molecule. High-energy electrons from NADH and FADH₂ drive proton pumping across the mitochondrial membrane, creating a proton gradient that powers ATP synthase to generate large quantities of ATP.
D. Krebs cycle: The Krebs cycle produces a small number of ATP molecules directly through substrate-level phosphorylation (1 ATP per cycle per acetyl-CoA). Its main contribution is generating NADH and FADH₂, which carry electrons to the electron transport chain for the production of most ATP.
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