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A guide RNA positions Cas9 at a chosen genomic sequence. What is the direct catalytic action of Cas9? A. Joining amino acids at a ribosome B. Methylating every cytosine in the genome C. Cleaving the targeted DNA strands D. Copying the guide RNA into a whole…
A cell drawing shows a nucleus whose actual diameter PQ is 6.0 μm. Use the millimetre ruler aligned with the drawing to measure PQ. What is the magnification? A. 30× B. 300× C. 3000× D. 30 000×
An early genetic system would need both information storage and reactions that use that information. Which observation strengthens the RNA-first hypothesis? A. Every RNA molecule forms a permanent double helix B. Ribose is absent from living cells C. RNA…
Which feature explains why a virus particle is not considered an independently living cell? A. It has no autonomous metabolism B. It contains no inherited information C. It cannot change through evolution D. Its genome can never be copied
A researcher freezes a cell sample and splits membranes before electron imaging. Which feature is this technique particularly useful for examining? A. The nucleotide sequence of a chromosome B. The distribution of structures embedded within the lipid bilayer…
A reconstruction of the classic Miller–Urey apparatus passes a reducing gas mixture over heated water. Which mixture matches the original experiment? A. Methane, ammonia, hydrogen and water vapour B. Methane, nitrogen, oxygen and water vapour C. Carbon…
Descendants of a single-celled alga remain attached after division and form a coordinated multicellular body. Consider these claims. I. Division of labour can develop between its cells. II. The body can be larger than one cell. III. The cells must now belong…
At constant temperature, I represents simple diffusion and II represents channel-mediated diffusion. Which interpretation of the labelled positions is valid? A. At W, the particles have lost most of their thermal energy B. At X, the finite number of channels…
Which cells have the developmental potential to generate both an embryo and its supporting extra-embryonic tissues? A. Stem cells restricted to replacing intestinal epithelium B. Cells from the earliest cleavage stages of an animal embryo C. Blood-forming stem…
Which evidence is most relevant when reconstructing a possible hydrothermal-vent setting for LUCA? A. A living individual has been certified as the unchanged LUCA B. Molecular comparisons reveal shared ancient sequences among prokaryotic lineages adapted to…