Which of the following diseases belongs to the same category as colourblindness in man?

What does the given symbol indicate?

Hemophilia is a/an.....

Colour blindness is found more in males than in females because

$A$ man and a woman who do not show any apparent symptoms of certain genetic diseases have seven children ($2$ daughters and $5$ sons). Three of the sons suffer from the given disease,but none of the daughters are affected. Which type of inheritance pattern do you suggest for this disease?

Mendelian disorders may be of which type?