IB DP Biology- D1.2 Protein synthesis- IB Style Questions For SL Paper 2 - FA 2025

(a)
Chromosome behaviour during mitosis ensures genetic identity through:
1. DNA replication in interphase produces two genetically identical sister chromatids per chromosome.
2. Chromosomes condense and become visible during prophase.
3. Chromosomes align at the metaphase plate and attach to spindle fibres during metaphase.
4. Sister chromatids separate and are pulled apart by shortening microtubules during anaphase.
5. Chromatids move to opposite poles during telophase, ensuring one identical copy in each daughter cell.
✅ Answer: Four key points required for full marks.

(b)
mRNA production (transcription) in the nucleus involves:
1. RNA polymerase unwinds DNA and breaks hydrogen bonds.
2. DNA template/antisense strand is used as a pattern.
3. Free RNA nucleotides are added to the growing mRNA strand.
4. Complementary base pairing occurs (A–U, G–C).
5. RNA polymerase joins nucleotides forming phosphodiester bonds.
6. RNA polymerase/mRNA detaches when reaching the stop signal, and DNA strands reattach.
✅ Answer: Four key points required for full marks.

(c)
Arterial adaptations (high-pressure blood flow):
– Narrow lumen to maintain high blood pressure.
– Thick walls with collagen for strength and protection against high pressure.
– Muscle tissue to withstand pressure and control diameter.
– Elastic tissue that stretches and recoils to maintain pressure and smooth blood flow.
Venous adaptations (low-pressure blood flow):
– Pocket valves to prevent backflow of blood.
– Thin, flexible walls that can be compressed by skeletal muscle to assist blood flow.
– Large lumen to reduce resistance to blood flow.
Common adaptation:
– Smooth endothelium lining to reduce friction and increase blood flow efficiency.
✅ Answer: Multiple structural adaptations with functional explanations required for full marks.