Question

All the seven children of a couple are males. What is the probability that the eight children will also be male?
(a) 1/2
(b) 1/4
(c) 1/8
(d) 1/16

Answer 1

Hint: Multicellular organisms have special cells called gametes for reproduction which contain only half the number of chromosomes. So when gametes from two different parents combine during reproduction, it results in a new individual, which contains DNA (the genetic material passed from parents) and a re-established number of chromosomes.

Complete answer:
The molecule of a DNA (deoxyribonucleic acid) which contains a part or all of the genetic material of an organism is called Chromosome. Humans usually have 23 pairs of chromosomes (or we can say a total of 46 chromosomes) . The autosomes (1-22 chromosome pairs) are the same in males and females. Chromosome pair 23 is dissimilar for males and females i.e. females have two X chromosomes, whereas males have an X chromosome and a much smaller Y chromosome. This 23rd pair determines the sex of the human. If the Y-chromosome in the zygote is inherited from the father then it is a male and if the X-chromosome is inherited from the father, the zygote will develop into a girl. So there is a 50% chance of the gender of the eight child as it depends on the father’s chromosomes and doesn’t depend on the previous siblings.

So, the correct answer is '1/2'.

Note:
X chromosome contains a large amount of euchromatin (a lightly packed form of chromatin) and a small amount of heterochromatin (condensed chromatin structure) whereas; Y chromosome contains a small amount of euchromatin and a large amount of heterochromatin. Genes present in the X chromosome shows criss cross inheritance and genes present in the Y chromosome shows linear inheritance.