Question

Sometimes it is observed that both parents are normal but they have a colour blind son.Expain how is it possible with the help of a cross

Answer 1

This is so bcoz the mother is a carrier of colour blind i.e., her genotype is X'Xand carrier feature is not shown in phenotype thus mother seems to be normal.
Father's genotype is XY
Now,as a result of a cross btwn them produces a colour blind son X'Y
Mo \ Fa___X______Y___ Thus a colour
X' !___X'X__!__X'Y___! blind son
X !___XX__!___XX__!