Thanawiya Amma (Egypt) · Physical and Natural Sciences

Biology and Genetics

28 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 28 questions

  1. A cell measures 2 μm in reality. In a micrograph it measures 0.8 mm. What is the magnification? (1 mm = 1000 μm)
  2. In a sample of double-stranded DNA, 21% of the bases are adenine. What percentage are guanine?
  3. What is the surface-area-to-volume ratio of a cube-shaped cell of side 5 μm?
  4. A food chain is grass → grasshopper → frog → snake. If the grass fixes 20000 kJ and about 10% of energy passes up each level, how much energy reaches the snake?
  5. A cell measures 2 μm in reality. In a micrograph it measures 0.4 mm. What is the magnification? (1 mm = 1000 μm)
  6. A cross produces phenotypes in the ratio 7:2. Out of 99 offspring, how many are expected in the second class?
  7. One bacterial cell divides by binary fission every 20 minutes. How many cells are there after 3 divisions, starting from one cell?
  8. A cell measures 2 μm in reality. In a micrograph it measures 0.2 mm. What is the magnification? (1 mm = 1000 μm)
  9. In a sample of double-stranded DNA, 22% of the bases are adenine. What percentage are guanine?
  10. In pea plants, tall (T) is dominant to short (t). A Tt plant is crossed with a tt plant. What is the probability that an offspring is homozygous recessive (tt)?
  11. What is the surface-area-to-volume ratio of a cube-shaped cell of side 2 μm?
  12. A cell measures 20 μm in reality. In a micrograph it measures 1 mm. What is the magnification? (1 mm = 1000 μm)
  13. A cross produces phenotypes in the ratio 6:7. Out of 364 offspring, how many are expected in the second class?
  14. One bacterial cell divides by binary fission every 20 minutes. How many cells are there after 8 divisions, starting from one cell?
  15. A cell measures 5 μm in reality. In a micrograph it measures 2 mm. What is the magnification? (1 mm = 1000 μm)
  16. In human ABO blood groups, the alleles I^A and I^B are codominant and the allele i is recessive. A father of blood group AB and a mother of blood group O have children. Which blood groups can their ch…
  17. In pea plants, round seeds (R) are dominant to wrinkled seeds (r) and yellow seeds (Y) are dominant to green seeds (y). Two plants heterozygous for both genes (RrYy) are crossed and produce 320 seeds.…
  18. Red-green colour blindness in humans is caused by a recessive allele on the X chromosome. A woman with normal vision, whose father was colour-blind, marries a man with normal vision. What is the proba…
  19. In guinea pigs, black coat (B) is dominant to white coat (b). A black guinea pig is crossed with a white guinea pig, and some of the offspring are white. What is the genotype of the black parent?
  20. Why is DNA replication described as semi-conservative?
  21. A stretch of mRNA contains 90 nucleotides, all of which are translated into protein. How many amino acids does this stretch code for?
  22. In the genetic code, how many different codons can be made from the four RNA bases taken three at a time?
  23. Which hormone, secreted by the beta cells of the islets of Langerhans in the pancreas, lowers the level of glucose in the blood?
  24. When a nerve impulse passes along an axon, what causes the membrane to depolarise?
  25. Which cells of the human immune system produce antibodies?
  26. During the contraction of a skeletal muscle, which ions are released from the sarcoplasmic reticulum so that myosin heads can bind to actin?
  27. In which part of the chloroplast do the light-dependent reactions of photosynthesis take place?
  28. A human body cell with 46 chromosomes divides by meiosis. What does the division produce?

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