Medical University Entrance Examination (Bulgaria) · Human Biology and Physiology

Cellular Biology and Molecular Genetics

35 practice questions, each with the answer and an explanation.

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Random questions from this topic, one at a time. You see the answer and the explanation straight after each one.

All 35 questions

  1. What is the primary role of cholesterol in mammalian plasma membranes at low temperatures?
  2. Which stoichiometry characterizes one complete cycle of the Na+/K+-ATPase pump?
  3. How does D-glucose cross the apical membrane of small intestinal enterocytes?
  4. Which protein complex forms the coat of vesicles involved in receptor-mediated endocytosis of LDL?
  5. In which cellular subcompartment does oxidative decarboxylation of pyruvate to acetyl-CoA take place?
  6. Which respiratory chain complex transfers electrons directly to molecular oxygen in mitochondria?
  7. Release of which mitochondrial intermembrane protein into the cytosol triggers intrinsic apoptosis?
  8. Deficiency of which lysosomal hydrolase causes Tay-Sachs disease and accumulation of GM2 ganglioside?
  9. Which organelle carries out beta-oxidation of very long-chain fatty acids (VLCFAs) containing 22 or more carbons?
  10. Which histone core octamer composition packages eukaryotic DNA into a nucleosome particle?
  11. Which enzyme unwinds the double helix at the replication fork by breaking hydrogen bonds?
  12. What is the function of topoisomerase II (DNA gyrase in bacteria) during DNA replication?
  13. Why are Okazaki fragments formed along the lagging strand during DNA replication?
  14. Which enzymatic activity allows DNA polymerases to excise mispaired bases immediately during replication?
  15. What is the primary biological role of telomerase in human germline cells?
  16. Which DNA repair pathway corrects bulky helix-distorting lesions such as UV-induced thymine dimers?
  17. Which RNA polymerase synthesizes messenger RNA (mRNA) precursors in human cells?
  18. Which consensus sequence located approximately 25 to 30 base pairs upstream of transcription serves as a core promoter in eukaryotes?
  19. What chemical modification constitutes the 5' cap added to eukaryotic pre-mRNA?
  20. Which ribonucleoprotein complex excises introns from eukaryotic precursor messenger RNA?
  21. What amino acid is specified by the universal initiation codon AUG in eukaryotic cytoplasm?
  22. Which trinucleotide trinucleotide sequence terminates polypeptide elongation across standard genetic codes?
  23. What is the biological meaning of degeneracy (redundancy) in the genetic code?
  24. Where does the amino acid attach on a mature transfer RNA (tRNA) molecule?
  25. Which ribosomal site receives an incoming aminoacyl-tRNA during the elongation cycle?
  26. During which phase of the eukaryotic cell cycle does semi-conservative DNA replication occur?
  27. Which protein acts as the 'guardian of the genome' by arresting the cell cycle at the G1/S checkpoint in response to DNA damage?
  28. How does hyperphosphorylation of retinoblastoma protein (pRb) promote progression through the G1/S checkpoint?
  29. During which stage of mitosis do sister chromatids disjoin and migrate toward opposite spindle poles?
  30. During which meiotic stage does crossing over (homologous genetic recombination) occur?
  31. How many functional spermatozoa develop from a single primary spermatocyte at the conclusion of meiosis?
  32. At which developmental stage is human oogenesis arrested from fetal life until ovulation at puberty?
  33. What is the expected phenotypic ratio in the F2 generation of a classic Mendelian monohybrid cross with complete dominance?
  34. Which chromosomal constitution characterizes an individual diagnosed with Klinefelter syndrome?
  35. What is the probability that a carrier female (XAXa) and an unaffected male (XAY) will have a son affected by an X-linked recessive disorder such as hemophilia A?

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