Trap 1: Phenotypic vs Genotypic Ratio Confusion

• Error: Stating phenotypic ratio = 1:2:1 in complete dominance
• Correct: Phenotypic = 3:1 (TT and Tt look identical); Genotypic = 1:2:1

Trap 2: Seed Colour vs Pod Colour Dominance

• Error: Assuming Yellow is dominant for BOTH seed colour and pod colour
• Correct: Yellow seeds are dominant; but GREEN pods are dominant. Green seed is recessive; Yellow pod is recessive.

Trap 3: Incomplete Dominance vs Co-dominance

• Error: Calling pink snapdragons an example of co-dominance
• Correct: Pink snapdragons = INCOMPLETE dominance (blended intermediate phenotype). AB blood group = CO-dominance (both phenotypes simultaneously expressed, not blended).

Trap 4: Pleiotropy vs Polygenic Confusion (Reversed)

• Error: Stating "polygenic = one gene, many traits"
• Correct: Pleiotropy = one gene → many traits (sickle cell HbS). Polygenic = many genes → one trait (skin colour). The "plei" prefix means "many effects"; "poly" prefix means "many genes."

Trap 5: Law of Independent Assortment Applied to Linked Genes

• Error: Applying 9:3:3:1 ratio to crosses involving genes on the same chromosome
• Correct: Independent assortment ONLY applies to genes on different (non-homologous) chromosomes. Linked genes deviate from 9:3:3:1 toward parental-class enrichment.

Trap 6: AB × O Cannot Produce O Offspring

• Error: Believing AB × O can produce AB and O children
• Correct: AB parent ($I^A$ $I^B$) contributes only $I^A$ or $I^B$ gametes. O parent (ii) contributes only i. Children = $I^A$ i (group A) and $I^B$ i (group B) ONLY. No AB and no O offspring are possible.

Trap 7: Test Cross vs Back Cross Confusion

• Error: Using "test cross" and "back cross" interchangeably
• Correct: Back cross = F1 crossed with any parent. Test cross = F1 specifically crossed with homozygous RECESSIVE parent. All test crosses are back crosses; not vice versa.

Trap 8: Recombination Frequency > 50% is Impossible

• Error: Calculating or accepting recombination frequencies above 50%
• Correct: Maximum observable recombination frequency is 50% (equivalent to independent assortment). Genes more than 50 cM apart still appear unlinked because multiple crossovers reduce apparent recombination.

Trap 9: Multiple Alleles = Individual Has 3 Alleles

• Error: Stating that multiple allelism means one person has three alleles
• Correct: Multiple alleles refers to more than two allelic variants existing in a POPULATION. Any individual diploid organism still carries only TWO alleles (one per chromosome). ABO has three population alleles; each person has two.

Trap 10: 9:3:3:1 Ratio for All Dihybrid F2 Crosses

• Error: Applying 9:3:3:1 to ALL dihybrid F2 crosses
• Correct: 9:3:3:1 applies ONLY when genes are on different chromosomes AND show complete dominance with no gene interaction. If genes interact epistatically, the ratio is modified (9:7, 9:3:4, 12:3:1, 15:1, or 13:3).