Question

If a couple has two boys and one girl, the probability of the next girl child to be born is
A. \[\frac{1}{4}\]
B. $\frac{1}{3}$
C. $\frac{1}{2}$
D. $\frac{2}{3}$
E. $\frac{3}{4}$

Answer 1

Hint: The biological system that determines the development of sexual characteristics in an organism is called sex determination. In human beings, females have two same kinds of sex chromosome, whereas, males have two different chromosome sets.

Complete answer: A biological system in which sexual characteristics in an organism can be determined is called sex-determination. Offsprings are produced by sexual reproduction with each organism having two sets of chromosomes. Sexual morphology can be specified as males and females having different alleles or even different genes. Differences in chromosome help in the determination of sexes of an organism. XO, ZO, XY, XZ, chromosomes, or haplodiploidy are different combinations of chromosomes which help in the determination of sex. XX/YY sex chromosomes are found in most of the organisms including humans. In humans, the male individual consists of two different sets of chromosomes that are XY and in females, they have two same sets of chromosomes that are XX. Depending on which chromosome is inherited from the father, the sex of the offspring is determined. If X chromosome is inherited, it results in the birth of a daughter and if a Y chromosome is inherited, it results in the birth of a son with XY chromosome and one X chromosome is inherited from mother. Therefore, the probability of the next girl child to be formed is 50 percent.
So, option C is the correct answer.

Note: Sex of the foetus is determined by an environmental variable such as temperature in some species. Example, the incubation temperature before hatching determines the sex of an organism. High incubation temperature results in male offspring in lizards.