Question

Which one of the following in man is controlled by dominant genes?

• A. Colour blindness
• B. Brachydactyly
• C. Nyctalopia
• D. Juvenile glaucoma

Answer 1

The correct option is B Brachydactyly

Night blindness is impaired ability to see in dim light, it is an autosomal disorder caused by mutations in genes that code for retina proteins involved in sending (transmitting) visual signals from rod cells bipolar cells, responsible for vision in dim light.

Juvenile glaucoma (JG) is a rare autosomal dominant open angle glaucoma, characterized by increased intra ocular pressure leading to optic nerve excavation and, when untreated, causing visual impairment. It is an autosomal recessive trait caused by mutations in genes that control the outflow of aqueous humor through the trabecular meshwork and into the Schlemm canal.

Brachydactyly is characterized by presence of unusually short fingers and toes. It is an autosomal dominant trait with variable expressivity and penetrance.

Colour blindness is a X-linked recessive disorder which is caused by presence of faulty cone cells which are responsible for colour perception.

So, the correct answer is option B.