Law of Dominance — Prelims Strategy

Prelims Strategy

To effectively tackle NEET questions on the Law of Dominance, start by firmly grasping its definition and the three key postulates. Always remember that in complete dominance, the F1 generation from a cross of pure parents will uniformly express the dominant trait.

For the F2 generation (from F1 x F1 cross), the phenotypic ratio will be 3:1 (dominant:recessive), and the genotypic ratio will be 1:2:1 (homozygous dominant:heterozygous:homozygous recessive). Practice drawing Punnett squares for monohybrid crosses to quickly visualize and calculate ratios.

Pay close attention to keywords like 'pure-breeding,' 'homozygous,' 'heterozygous,' 'F1 generation,' and 'F2 generation.

Crucially, be prepared to differentiate the Law of Dominance from its exceptions: incomplete dominance (where F1 is intermediate, and F2 phenotypic ratio is 1:2:1) and co-dominance (where F1 expresses both traits, and F2 phenotypic ratio is 1:2:1).

Many trap options in MCQs will present scenarios of these exceptions. Always identify if the question implies complete masking or an intermediate/simultaneous expression. For numerical problems, correctly assign alleles (e.

g., 'T' for tall, 't' for dwarf) and parental genotypes before setting up the cross. Double-check your calculations and ensure you're answering for the correct generation (F1 vs. F2) and type of ratio (phenotypic vs.

genotypic).