Sex Determination in HumansPractice Questions & MCQs

Q1. Consider the following statements about sex determination in humans: (I) Human females are XX. (II) The father determines the sex of the child. (III) Every egg carries a Y chromosome. Which of the above statement(s) is/are correct?

• A.None of these
• B.Only III
• C.Only I
• D.Only I and II

Answer: D. Only I and II

NCERT fact (biology, chapter 'Heredity'): An ionic bond forms when a metal donates electrons to a non-metal: e.g. Na -> Na+ + e-, Cl + e- -> Cl-, and Na+ + Cl- -> NaCl; the resulting solid is held by strong electrostatic attraction => this fixes the property asked in the stem; hence the answer = Only I and II. Why option D fits - Correct. Distractor analysis: option A) 'None of these' is incorrect: Re-check each statement individually; option B) 'Only III' is incorrect: Re-check each statement individually. Final answer - D) Only I and II.

Q2. Can you give examples for each of the categories of consumers?

• A.Herbivores: grasshoppers, carnivores: frogs, omnivores: humans, parasites: tapeworms.
• B.Herbivores: humans, carnivores: grasshoppers, omnivores: frogs, parasites: tapeworms.
• C.Herbivores: frogs, carnivores: humans, omnivores: grasshoppers, parasites: tapeworms.
• D.Herbivores: tapeworms, carnivores: humans, omnivores: grasshoppers, parasites: frogs.

Answer: A. Herbivores: grasshoppers, carnivores: frogs, omnivores: humans, parasites: tapeworms.

Eliminate first - option B) 'Herbivores: humans, carnivores: grasshoppers, omnivores: fr...' fails since The examples are incorrect; option C) 'Herbivores: frogs, carnivores: humans, omnivores: grasshopp...' doesn't hold - The examples are incorrect; option D) 'Herbivores: tapeworms, carnivores: humans, omnivores: grass...' doesn't hold - The examples are incorrect. That leaves only option A). Confirm with the chapter rule: Herbivores: grasshoppers, carnivores: frogs, omnivores: humans, parasites: tapeworms (biology, chapter 'Heredity'). Answer: A) Herbivores: grasshoppers, carnivores: frogs, omnivores: humans, parasites: tapeworms.

Q3. If an X-bearing sperm fertilises the egg, the child will be a:

• A.boy (XY)
• B.XO
• C.either
• D.girl (XX)

Answer: D. girl (XX)

Reading the problem, the numerical data stated in the question (biology, chapter 'Heredity'). What we must find: the requested quantity. The principle that connects these is - hence the answer = girl (XX). Sexual reproduction needs 2 parents and gametes. So the correct choice is D) girl (XX). As for the others, option A) 'boy (XY)' doesn't hold - X + X gives a girl (XX); option B) 'XO' is incorrect: Egg X + sperm X => XX (girl).