Test 104   (ocular genetics)

1. The following are true about retinoblastoma: 

a. in familial retinoblastoma, the hereditary pattern is that 
     of an autosomal dominant mutation 

b. the genetic defect is recessive at the cellular level 

c. retinoblastoma results from a dominant mutant 
    oncogene 

d. both germinal or somatic mutation can give rise to 
    retinoblastoma

e. osteosarcoma is associated with retinoblastoma 
    containing deletion of chromosome 13.

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A dominant mutant oncogene does not appear to be responsible for retinoblastoma.

2. The following are X-linked disorders:

a. choroideremia

b. Leber's amaurosis

c. ocular albinism

d. retinoschisis

e. Norrie's disease

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Leber's amaurosis is an autosomal recessive disorder.

 

3. The following structures are derived from the neuroectoderm:

a. lens

b. corneal endothelium

c. ciliary muscles

d. sclera

e. retinal pigment epithelium

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Lens is derived from ectoderm. Corneal endothelium, ciliary muscles, sclera and retinal pigment epithelium are derived from neuroectoderm.

4. Cataract occurs in the following conditions:

a. Reiger's syndrome

b. Lowe's syndrome

c. trisomy 13 (Patau's syndrome)

d. congenital rubella

e. congenital toxoplasmosis

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Reiger's syndrome and congenital toxoplasmosis are not associated with cataract.

5. Features of foetal alcohol syndrome include:

a. microphthalmos.

b. coloboma

c. hypoplastic optic disc

d. narrow forehead

c. blepharophimosis

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In addition, there is strabismus, telecanthus and also anterior segment dysgenesis such as Peter's and Axenfeld's anomaly.

 
 

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