Albinism

Albinism

Q. 1 Albinism is due to deficiency of the following enzyme?

 A Phenylalanine hydroxylase

 B

Homogentisic acid oxidase

 C

Tyrosinase

 D

Decarboxylase

Q. 1

Albinism is due to deficiency of the following enzyme?

 A

Phenylalanine hydroxylase

 B

Homogentisic acid oxidase

 C

Tyrosinase

 D

Decarboxylase

Ans. C

Explanation:

The most common cause of albinism is a defect in tyrosinase, the enzyme most responsible for the synthesis of melanin. Albinism is an inborn error due to lack of synthesis of melanin. It is an autosomal recessive disorder with a frequency of 1 in 20,000.

Ref: Textbook of Biochemistry and Human Biology by G. P. Talwar, 3rd Ed, Page 452


Q. 2

In complete albinism the colour of iris is:

 A

White

 B

Black

 C

Pink

 D

Blue

Ans. C

Explanation:

Ans. Pink


Q. 3

All are seen in albinism except:

 A

Glaucoma

 B

Photophobia

 C

Refractive error

 D

Nystagmus

Ans. A

Explanation:

Ans. Glaucoma


Q. 4

All of the following are true regarding albinism except:    

March 2009

 A

Autosomal recessive condition

 B

Normal production of melanin

 C

Tyrosinase positive are usually less severe

 D

Prone to develop squamous cell carcinoma of skin

Ans. B

Explanation:

Ans. B: Normal production of melanin

Oculocutaneous albinism is inherited as an autosomal recessive trait.

Ocular albinism results from mutation in a gene on the X chromosome, which maps to band Xp22.3-22.2 and is inherited as an X-linked recessive trait.

Two main variants:

Tyrosinase positive are usually less severe whereas tyrosinase negative are more severe

Molecular defect is absent/sparse production of melanin.

Pateint presents with total absence of melanin in skin, hair and eyes.

They are prone to develop squamous cell carcinoma of skin induced by ultraviolet rays, which develops on photo-exposed parts due to lack of protective melanin.


Q. 5 Albinism is due to deficiency of ‑

 A Tyrosinase

 B

Tyrosine hydroxylase

 C

Tyrosine transaminase

 D

Cystine reductase

Ans. A

Explanation:

Q. 6

A child presents with albinism. He should be evaluated for:

 A

ENT consultation

 B

Eye consultation

 C

Electrocardiography

 D

Neurosurgery

Ans. B

Explanation:

Ans. b. Eye consultation

uoculocutaneans albinism We 1 (OCA I) is characterized by great reductinn in or absence of erosinase acttvily, OCAIA, the most
severcform, is characterized by a tack of visible pigment in hair, skir4 and eyes. This manifesi as photophobia, nystagmas, defective
visual acui4t, white hair, and white skin OCAIB, or yellow mutant albinism, manifests at birrh as white haiti pink skin, and gray e”ves.
OCA2 ranges from nearly normal to closely resembling type I albinism. This is the most commonform of albinism seen worldwidc.
Progressive improvement in visual ocuity and nystagmus occurs with aging


Q. 7

Enzyme deficient in occulocutaneous albinism type 1 is ‑

 A

Tyrosinase

 B

Pink protein

 C

Tyrosinase related protein 1

 D

Membrane associated transport protein (MATP)

Ans. A

Explanation:

Ans. is ‘a’ i.e., Tyrosinase


Q. 8

Specific for albinism 

 A

Red reflex

 B

Decreased visual activity

 C

Photophobia

 D

Nystagmus

Ans. A

Explanation:

Ans. is ‘a’ i.e., Red reflex 

  • All the given options are seen in albinism. But, red reflex is specific.
  • Ocular features in albinism –
  • a Red reflex
  • Pink or blue iris
  • Dazzling glare
  • Photophobia
  • Decreased vision
  • Nystagmus
  • Clear retinal and choroidal vessels, separated by glistening white space
  •  Strabismus (mild to moderate)


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