Genes as an explanation

Reductionism is the standard AO3 criticism, most often thrown away — explaining behaviour by its simplest parts, here reducing depression to the version of one gene. Three moves: name it; say what reduces to what; say why it matters (it omits life events and thinking style, so cannot explain why one person with the gene is depressed and another not).

The definition trap here costs part-marks. Nature = inherited, biological (genes, temperament). Nurture = environment and learning (life events, upbringing). The recorded failure is mechanical: the two parts answered the wrong way round, or nurture answered on nature. Stressful life events are nurture, even beside the gene — gene = nature, events = nurture.

Evaluation is examinable content here; the failure is identification without justification. Label: "a strength is scientific evidence." Explained: "it rests on objective evidence — twin studies count cases, which no researcher reinterprets, so figures reproduce." Force it with "and this matters because…" — unfinished, it is no point.

Carrying a gene version alongside a higher rate of a problem shows the two go together — a relationship. It does not show the gene produced the problem; another factor could raise both. This is a genuine AO3 point: twin, family and adoption studies show a problem runs with shared genes, but running-together is correlation, not cause.

Asked for the difference between nature and nurture, two definitions side by side leave it implied — worth one mark. A connective names the axis: "nature explains behaviour by inherited factors such as genes, whereas nurture explains it by environment such as life events." "Whereas", "while" or "in contrast" earns the second mark.

A higher rate in identical than non-identical pairs is the headline twin evidence — but it is not pure genetics. Identical twins are usually treated more alike, so their environments are more similar as well as their genes. Part of the higher concordance may come from shared upbringing, so the design confuses genes with environment — a strong AO3 weakness.

Two linked errors. "Inherit the gene → you get it": no — identical twins share all their genes, yet discordant pairs exist, so a gene alone cannot decide it. What is inherited is a raised likelihood. "If genetic, therapy is pointless": no — a vulnerability is still acted on through environment and behaviour, so deterministic is a criticism, not a fact.