Biology Flashcards
7 cards from real MCAT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Biology flashcards as text
Which of the following correctly describes the concept of epistasis?
Answer: One gene modifies or masks the expression of a gene at a different locus
Epistasis occurs when the expression of one gene (the epistatic gene) suppresses or modifies the phenotypic effect of another gene at a different locus.
A muscle cell at rest has a resting membrane potential of -90 mV. This value is primarily determined by:
Answer: The equilibrium potential for potassium
The resting membrane potential of muscle cells is closest to the Nernst equilibrium potential for K+ because membranes are most permeable to potassium at rest.
Which of the following is NOT a characteristic of stem cells?
Answer: Permanent withdrawal from the cell cycle
Stem cells are defined by their ability to self-renew and differentiate; permanent cell cycle withdrawal (terminal differentiation) is the opposite of a stem cell property.
During meiosis I, crossing over between homologous chromosomes occurs at which structure?
Answer: Synaptonemal complex/chiasmata
Crossing over (recombination) occurs at chiasmata within the synaptonemal complex during prophase I of meiosis, exchanging segments between homologous chromosomes.
Which of the following enzymes would be inhibited by a product of the citric acid cycle in a classic example of feedback inhibition?
Answer: Isocitrate dehydrogenase inhibited by NADH
Isocitrate dehydrogenase is allosterically inhibited by NADH (a product of the cycle), slowing the TCA cycle when the cell has sufficient reducing equivalents.
A researcher discovers a new virus that infects bacteria and integrates its genome into the host chromosome without immediately causing cell lysis. This virus is best classified as a:
Answer: Temperate phage
A temperate phage can enter lysogeny, integrating its genome as a prophage into the bacterial chromosome and replicating with the host without causing immediate lysis.
Which of the following correctly describes the role of the hypothalamus in body temperature regulation?
Answer: It acts as a thermostat, integrating temperature signals and initiating effector responses
The hypothalamus serves as the body's thermostat, receiving afferent temperature information and coordinating efferent responses (vasodilation, sweating, shivering) through the autonomic nervous system.