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Reproduction common mistakes
Study Reproduction with curriculum-aligned Common Mistakes resources, practice links, and exam-focused support.
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common mistakes
Resource type
Topic
Reproduction
Common mistakes
Misunderstanding Genetic Crosses
Students often confuse the process of carrying out a genetic cross with simply stating the sex chromosomes involved, failing to show the actual inheritance pattern.
Fix itTo fix this, students should practice drawing Punnett squares to illustrate the genetic cross, clearly indicating the parental gametes and the resulting offspring genotypes.
Misinterpreting Ratios in Sex‑Determination Crosses
Students often treat the 1:1 ratio of male to female offspring as a fixed rule, ignoring that the ratio depends on the sex of the parent and the specific cross (e.g., XX × XY vs. XY × XY).
Fix itExplain that the 1:1 ratio applies only when one parent contributes a single sex chromosome (XX or XY) and the other contributes a single sex chromosome (XY). Use a simple Punnett square to show how the ratio changes when both parents are XY (giving 1/4 XX, 1/2 XY, 1/4 YY) or when both are XX (all XX). Emphasise that the ratio is derived from the proportion of gametes, not a universal rule.
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