If a father and son are both defective in red-green colour vision,is it likely that the son inherited the trait from his father? Comment.

(N/A) The gene for red-green colour blindness is $X$-linked recessive.
In humans,a son inherits his $Y$-chromosome from his father and his $X$-chromosome from his mother.
Since the trait is $X$-linked,it cannot be passed directly from father to son.
Therefore,the son did not inherit the trait from his father.
In this case,the mother must be a carrier (heterozygous) for the colour blindness gene,and she passed the affected $X$-chromosome to her son.