What does the given symbol represent in a pedigree chart?

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.

If a color-blind man marries a normal woman,then regarding the vision of their offspring,which of the following is true?

The 'Thala test' is performed for the confirmation of:

Assertion $(A) :$ Phenylketonuria is an inborn error of metabolism and inherited as the autosomal dominant trait.
Reason $(R) :$ The disease is caused by mutation in the gene that codes for the enzyme phenylalanine hydroxylase.

Absence of teeth,bifid tongue and mental retardness are observed in . . . . . . .