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Biology Question 117 – NEET-UG 2024

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Which one of the following can be explained on the basis of Mendel's Law of Dominance? A. Out of one pair of factors one is dominant and the other is recessive. B. Alleles do not show any expression and both the characters appear as such in F2 generation. C. Factors occur in pairs in normal diploid plants. D. The discrete unit controlling a particular character is called factor. E. The expression of only one of the parental characters is found in a monohybrid cross. Choose the correct answer from the options given below:

This law describes how different alleles (factors) interact when present together in an individual, particularly in heterozygous conditions.

Step 1: Understand Mendel's Law of Dominance✦ Active

Mendel's Law of Dominance states that in a cross between two pure parents differing in one pair of contrasting characters, the character that expresses itself in the F1 generation is called the dominant character, and the one that remains unexpressed is called the recessive character. This law is often presented with foundational postulates: factors (alleles) are discrete units, and they occur in pairs.

💡 Teacher's Secret Hint

Remember that the Law of Dominance explains the expression pattern in heterozygotes and the reappearance of recessive traits in F2.

Step 2: Evaluate each statement based on the Law of Dominance○ Expand

A. "Out of one pair of factors one is dominant and the other is recessive." This is the core definition of dominance and recessiveness, directly explained by the Law of Dominance. (Correct) B. "Alleles do not show any expression and both the characters appear as such in F2 generation." This is incorrect. The dominant allele *does* show expression in F1, and the recessive character reappears in F2 because it was masked in F1, not because alleles show no expression. (Incorrect) C. "Factors occur in pairs in normal diploid plants." This is a fundamental postulate of Mendelian inheritance, often considered part of the broader context of the Law of Dominance. (Correct) D. "The discrete unit controlling a particular character is called factor." This is also a fundamental postulate, defining the "factor" (gene/allele), and is foundational to understanding dominance. (Correct) E. "The expression of only one of the parental characters is found in a monohybrid cross." This observation in the F1 generation is a direct consequence and explanation of the Law of Dominance. (Correct)

💡 Teacher's Secret Hint

Distinguish between the core principle of dominance and the foundational postulates that enable it.

Step 3: Select the correct combination○ Expand

Based on the evaluation, statements A, C, D, and E are consistent with or explained by Mendel's Law of Dominance. Therefore, the correct option is (1) A, C, D and E only.

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