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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.

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  1. Which of the following structures is responsible for ribosome biogenesis in eukaryotic cells?

    Answer: Nucleolus

    The nucleolus is the site within the nucleus where rRNA genes are transcribed and ribosomal subunits are assembled before being exported to the cytoplasm.

  2. A patient has a genetic defect causing dysfunction of cilia in airway epithelial cells. Which cellular process is most likely impaired?

    Answer: Mucociliary clearance of debris

    Ciliary movement in airway epithelium drives mucociliary clearance, propelling mucus and trapped particles toward the throat for removal.

  3. In Mendelian genetics, two heterozygous parents (Aa × Aa) produce offspring. What fraction of offspring would display the recessive phenotype?

    Answer: 1/4

    A monohybrid cross of Aa × Aa yields a 3:1 phenotypic ratio (3 dominant: 1 recessive), so 1/4 of offspring display the recessive phenotype (aa).

  4. Which of the following best describes the role of ubiquitin in cellular protein degradation?

    Answer: It tags proteins for recognition and degradation by the proteasome

    Ubiquitin is covalently attached to lysine residues of target proteins, marking them for recognition by the 26S proteasome for degradation.

  5. A researcher crosses true-breeding red flowers with true-breeding white flowers and obtains all pink flowers in F1. This result is best explained by:

    Answer: Incomplete dominance

    Incomplete dominance produces a blended intermediate phenotype (pink) in heterozygotes because neither allele is fully dominant over the other.

  6. Which of the following correctly describes the orientation of translation?

    Answer: 5'→3' reading of mRNA with protein synthesis N-terminus to C-terminus

    Ribosomes read mRNA in the 5'→3' direction and synthesize polypeptides from the amino terminus (N) to the carboxyl terminus (C).

  7. Which blood vessel has the lowest oxygen content under normal physiological conditions?

    Answer: Pulmonary artery

    The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs, making it the vessel with the lowest oxygen content in the systemic circulation.