Question

Five Mark Questions :
(a) Why are colour blindness and thalassemia categorized as Mendelian disorders? Write the symptoms of these diseases seen in people suffering from them.
(b) About 8% of the human male population suffers from colour-blindness whereas only about 0.4% of the human female population suffers from this disease. Write an explanation to show how it is possible.

Answer 1

(a)Thalassemia and color blindness are categorized as Mendelian disorders because these disorders are alterations or mutations in a single gene. These are transmitted through Mendelian principles of inheritance.
Symptoms of Thalassemia:
1. Dark urine
2. Bone deformities
3. Yellow skin
Symptoms of Colour blindness
1. Difficulty in identifying the brightness of different color

2. Inability to tell the difference between shades of the same or similar colors, particularly red and green.

(b) Colour blindness is a sex-linked disorder and is caused by a recessive gene located on the X chromosome. The Y chromosome of male does not carry any gene for color vision and the defect appears in the presence of a single recessive gene (XY). As a result, color blindness is more common in males (8%) as compared to females (0.4%).