• Testcross Phenotypes for a Polyhybrid Genotype:
• Genotype of the individual: $AaBbCcDd$ (heterozygous at $n = 4$ independently assorting gene loci).
• Testcross involves crossing with a homozygous recessive tester: $AaBbCcDd \times aabbccdd$.
• For each independent gene locus under complete dominance, the testcross produces 2 phenotypic classes:
• $Aa \times aa \to 1\,A\_ : 1\,aa$ (2 phenotypes)
• $Bb \times bb \to 1\,B\_ : 1\,bb$ (2 phenotypes)
• $Cc \times cc \to 1\,C\_ : 1\,cc$ (2 phenotypes)
• $Dd \times dd \to 1\,D\_ : 1\,dd$ (2 phenotypes)
• Total number of distinct phenotypic classes in the testcross progeny is:

• Conclusion: 16 distinct phenotypes appear in the testcross progeny (Option 1).

Correct option: (1) 16