The short answer
Read a DNA-content trace or a cell-sorting histogram, name the stage a cell is held in, and say what that block implies.
Written and checked by GAMSAT tutors — not AI-generated.
Try the reasoning style
We treat forgetting as a failure — a lapse to be patched with reminders and records. Yet a mind that kept everything could not think; it would drown in the undifferentiated noise of every moment it had ever lived. To forget is not so much to lose information as to decide, mostly without our noticing, what was never worth keeping.
The author's argument relies most directly on which unstated assumption?
Pick an option to see how the tutor reasons to the answer — not just whether you were right.
Not quite — the answer is B.
Work backwards from the conclusion: a mind that ‘kept everything’ supposedly ‘could not think.’ That only follows if thinking means leaving most of experience out — so B is the premise the argument quietly rests on. A raises reliability, which the passage never weighs; C contradicts ‘mostly without our noticing’; D smuggles in a claim about intellect the passage never makes. The question rewards finding the hidden premise, not recalling a fact.
Section III rarely asks you to name the phases. It gives you a DNA trace or a sorted population and asks what a block implies. It turns on one distinction: chromosome number and DNA content are separate counters.
Two counters
Count chromosomes by centromeres: one centromere, one chromosome, however many chromatids hang off it. Count DNA in C: a human G1 cell is 2C, 46 chromosomes. S phase doubles DNA and leaves chromosome number alone; anaphase does the reverse. Only cytokinesis halves both.
- DNA content
- Chromosome number
The two mistakes
"After S phase the cell has 92 chromosomes." No: 46 chromosomes, 92 chromatids — an option list offering both is testing exactly that.
"4C means tetraploid." Ploidy counts sets, not DNA: a G2 human cell is 4C and diploid.
Reading an arrest
The move
Cells pile up on the near side of the step they cannot take. Find the pile-up, then name the transition just after it.
A 2C pile-up
Held at G1/S, before replication.
A 4C pile-up
Held at G2/M or inside mitosis. Condensed chromosomes and no nuclear envelope mean mitosis; they need not be aligned, since a microtubule blocker leaves them scattered.
- untreated
- + compound, 18 h
Reading the histogram
Figure 2: what has the compound done, and what can you not conclude?
Check yourself
A drug inactivates separase, the enzyme that cuts the protein ring holding sister chromatids together. Cells of an organism with 2n = 8 are grown in the drug and then sampled. A treated cell that has entered mitosis contains:
Key takeaways
- One centromere is one chromosome; sister chromatids do not count separately.
- S doubles DNA, not chromosome number; anaphase does the reverse.
- 4C is G2 or mitosis; DNA content alone cannot separate them.
- Cells pile up before the step they cannot take; name the transition just after it.
Practise this with real GAMSAT-style questions
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