The short answer
The central dogma, base pairing, codons and reading frames — enough to reason through any sequence question.
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.
The central dogma is the flow of genetic information: DNA → (transcription) → mRNA → (translation) → protein. GAMSAT rarely asks you to recall it cold — it gives you a sequence and asks you to reason. Master base pairing and codon reading and you can handle those.
Base pairing is the whole trick
DNA pairs A–T and G–C. In RNA, uracil (U) replaces thymine (T), so transcription pairs DNA's A with RNA's U. Transcription reads the template strand and builds an mRNA that matches the coding strand (with U for T).
Watch the strand and the frame
Two easy slips: (1) transcribing the coding strand instead of the template strand, and (2) losing the reading frame — codons are read in non-overlapping groups of three from a fixed start. Shift by one base and every downstream codon changes.
From DNA to amino acids
1. Transcribe
Read the template strand 3'→5'; build mRNA 5'→3' by complementary pairing (A→U, T→A, G→C, C→G).
2. Split into codons
Group the mRNA into threes from the start codon (AUG). Each codon = one amino acid.
3. Translate
Use the codon table to read each triplet into an amino acid. A stop codon (UAA/UAG/UGA) ends the chain.
Worked example
A DNA template strand reads 3'-TAC-5'. What mRNA codon does it produce, and what does that codon signal?
Check yourself
A single base is inserted near the start of a coding sequence. What is the most likely consequence?
Key takeaways
- Central dogma: DNA → mRNA (transcription) → protein (translation).
- Pairing: A–T and G–C in DNA; U replaces T in RNA.
- Transcription reads the template strand; the mRNA matches the coding strand (with U).
- Codons are non-overlapping triplets read from AUG (start); UAA/UAG/UGA stop.
- Insert/delete one base ⇒ frameshift ⇒ everything downstream changes.
Practise this with real GAMSAT-style questions
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