Question

Match List I with List II regarding patterns of inheritance:  

List I	List II
A. Incomplete dominance  B. Co-dominance  C. Pleiotropy  D. Polygenic inheritance	I. Human skin colour  II. Inheritance of flower colour in Antirrhinum sp.  III. Phenylketonuria disease in humans  IV. ABO blood groups

Choose the correct answer from the options given below:

• A. A-II, B-IV, C-III, D-I
• B. A-I, B-IV, C-III, D-II
• C. A-I, B-III, C-II, D-IV
• D. A-II, B-I, C-III, D-IV

Hint:

\textbf{P}leiotropy = \textbf{1} Gene $\rightarrow$ \textbf{Many} Effects. \textbf{P}olygenic = \textbf{Many} Genes $\rightarrow$ \textbf{1} Effect. Don't flip these two!

Answer 1

The Correct Option is A

Genetic inheritance often deviates from simple Mendelian dominance. The following examples are classic NEET cases:
• Incomplete Dominance: Seen in Antirrhinum majus (Snapdragon). Here, the $F_1$ phenotype is an intermediate between the two parents (e.g., Red $\times$ White = Pink).
• Co-dominance: The ABO blood grouping in humans is a prime example where both alleles $I^A$ and $I^B$ are fully expressed in the $AB$ phenotype.
• Pleiotropy: This occurs when a single gene influences multiple phenotypic traits. Phenylketonuria (PKU) is caused by a single gene mutation but results in mental retardation, skin pigmentation changes, and hair reduction.
• Polygenic Inheritance: This involves multiple genes controlling a single trait, leading to a gradient of phenotypes. Human skin colour is the standard example, controlled by at least three genes.