विस्तृत व्याख्या:

Penetrance vs. Expressivity (प्रवेश्यता बनाम अभिव्यक्तित्व):

• Penetrance (प्रवेश्यता): The proportion of individuals carrying a particular genotype who actually manifest the corresponding phenotype. When individuals possessing the genotype fail to express the phenotype, the trait exhibits Incomplete Penetrance (अपूर्ण प्रवेश्यता).
• Expressivity (अभिव्यक्तित्व): The degree or intensity with which a genotype is expressed phenotypically among individuals showing the trait (e.g., polydactyly having varied numbers of extra digits).
• Co-dominance (सह-प्रभाविता): Both alleles are expressed equally in the heterozygote (e.g., AB blood group).
• Partial dominance (आंशिक प्रभाविता / Incomplete dominance): Heterozygote has an intermediate phenotype (e.g., pink flowers in Mirabilis jalapa).

Correct Answer: Option 2 (Incomplete penetrance).