Which symbol is used in pedigree analysis to represent a carrier offspring?

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 . . . . . . .

Hemophilia is more commonly observed in human males than in human females because ....

Myotonic dystrophy is which type of trait?

$A$ boy is colour blind. Among his two sisters,one is colour blind and one is a carrier (normal). Who is colour blind in his family?