610 exam-style questions on Continuity and change with answers and explanations. Six real samples below — the full set is free with an account.
The Meselson-Stahl experiment demonstrated that DNA replication is:
Answer: Semi-conservative
Using heavy and light nitrogen isotopes, Meselson and Stahl showed each new DNA molecule contains one original and one newly synthesised strand, confirming the semi-conservative model.
The genetic code is described as 'degenerate' because:
Answer: Several codons can specify one amino acid
Degeneracy means several different codons can specify the same amino acid (e.g. six codons for leucine). This reduces the effect of some point mutations on the resulting protein.
In eukaryotes, which mechanism can switch genes off without changing the DNA base sequence?
Answer: Methylation of DNA
Epigenetic methylation of cytosine bases (and histone modification) can silence genes by preventing transcription, without altering the underlying nucleotide sequence, and can sometimes be inherited.
A dihybrid cross between two heterozygotes for two unlinked genes, each showing complete dominance (AaBb × AaBb), gives which phenotypic ratio?
Answer: 9:3:3:1
With independent assortment of two gene pairs, the offspring show the classic 9:3:3:1 ratio of the four phenotype combinations, reflecting Mendel's law of independent assortment.
A test cross is used to determine whether an organism showing a dominant phenotype is homozygous or heterozygous by crossing it with an individual that is:
Answer: Homozygous recessive
Crossing with a homozygous recessive individual reveals the unknown genotype: if any recessive offspring appear, the parent must be heterozygous; if all offspring show the dominant trait, it is likely homozygous.
A recombination frequency of 10% between two linked genes indicates that they are:
Answer: Close together on the same chromosome
Recombination frequency reflects distance between loci; 10% recombinants means the genes are relatively close (about 10 map units apart), since crossing over between nearby loci is less likely.
That was 6 of 610 Continuity and change questions.
Practise all 610 freeA student claims that because self-pollinating plant populations show low genetic variation, self-pollination directly causes harmful mutations.
See the correction →StateAO1 · 1–2 marks
One word or one short sentence. No explanation, no working: the mark is for the fact itself.
OutlineAO2 · 1–4 marks
A brief account or summary: the main points in two or three sentences, no evaluation.
DistinguishAO2 · 1–4 marks
Make the difference clear for BOTH terms — a definition of one of them is only half an answer.
610 Continuity and change questions — free with an account. Spaced repetition, streaks and full exam simulations included.
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