Genetics

Traps in Genetics

• Reverses a direction, order or effect
  Before answering, say the process out loud in order with arrows (receptor → sensory → relay → motor → effector; lungs → pulmonary vein → left atrium). Then ask: does my option point the same way? If an option is the mirror image of a fact you know, it is a trap.
• Over-generalises a rule to all cases
  Absolute words (all, always, every, never) are rarely right in biology. Try to name one exception; if you can, reject the option.
• Takes one contributing factor as the whole answer
  Watch for 'only', 'just', 'mainly'. Ask: is this the MAIN reason, or one contributor? If it would need other things to work (plasma proteins need platelets), it is incomplete.
• Uses an everyday idea instead of the biology
  Translate everyday words into the textbook definition before choosing. If the only reason an option attracts you is its name or looks, test it against the definition in the stem.
• Errors in monohybrid ratios
  Draw the Punnett square every time. Any genotype with ONE dominant allele shows the dominant trait: TT and Tt are both tall. Tt × Tt → 3 : 1.
• Confuses genotype and phenotype
  Genotype = the alleles (Tt). Phenotype = what you see (tall). "PHenotype = PHysical".
• Confuses continuous and discontinuous variation
  Continuous: range of values, many genes + environment (height, weight). Discontinuous: distinct categories, few genes (blood group, tongue rolling).
• Chooses a true but irrelevant statement
  Re-read the question word (why, which, where, what causes). An option can be a true fact and still be wrong because it answers a different question.
• Explains by need or purpose
  Variation comes first (by chance mutation and sexual reproduction); selection then favours what already exists. Replace 'it needs to' with 'individuals that happened to have it survived and reproduced more'.
• Mixes up a pair of similar technical terms
  Make a two-column table for each confusable pair with one defining feature each, and a memory hook (aTLas holds the 'world' (skull) and nods; aXis lets you shake 'no'). Underline the defining feature the stem gives before you look at the options.
• Gives the job of a neighbouring structure or stage
  Learn structures as pairs of 'name → one job' and contrast neighbours: ribosome makes protein, mitochondrion releases energy; cochlea hears, semicircular canals balance. When two options sit in the same organ or process, ask which one does exactly the job in the stem.
• Puts an example in the wrong group
  Classify by the defining features in the key, not by habitat or name: mammals have hair and mammary glands; true fruits come from the ovary only. Check each option against the defining feature in turn.
• Confuses organelle functions
  Nucleus: controls activities, holds DNA. Mitochondrion: aerobic respiration. Ribosome: protein synthesis. Chloroplast: photosynthesis. Cell membrane: selectively permeable. Cell wall (cellulose): support. Vacuole: cell sap, turgor.