Experiment 20 — Who Decides the Sex of the Child?

Topic: Biology · Class 10 · Heredity: sex determination in humans

Aim: Work out the probability of a girl from a Punnett square — and settle a common myth.

Daily: In India this is not only biology. The belief that a woman is responsible for the sex of her child has caused real harm to real families, and the science answers it plainly.

Question: Which parent’s gamete determines the sex of a human child?

Exp: All eggs carry X; sperm carry either X or Y.

Question: A human female has sex chromosomes…

Exp: So every egg carries an X.

Question: The probability of a boy at each conception is…

Question: After three daughters, the chance the fourth child is a boy is…

Exp: Each conception is independent.

Question: In many reptiles, sex is determined by…

Exp: Not all species use chromosomal determination.

Question: A 6 V supply drives 0.5 A through a resistor. Its resistance is…

Question: Three 6 Ω lamps in parallel across 6 V draw a total current of…

Exp: Each draws 1 A; the currents add.

Question: A 1000 W heater on 220 V draws about…

Question: The split-ring commutator in a motor…

Exp: It keeps the rotation continuous.

Question: Induced emf is largest when the magnet moves…

Exp: A faster change in flux induces more emf.

Question: An object at 2F in front of a convex lens gives an image that is…

Question: Myopia is corrected with a…

Exp: It diverges rays so they focus on the retina.

Question: Balance: 3Fe + 4H₂O → Fe₃O₄ + ? H₂

Exp: 8 hydrogen atoms on the left need 4 H₂.

Exp: It is too reactive for carbon reduction.

Question: Ionic compounds conduct electricity when…

Exp: Ions must be free to move.

Question: A saturated hydrocarbon with 5 carbons has how many hydrogens?

Question: Soap fails in hard water because it forms…