Test 172 (modified from MRCOphth Questions, 2003)
1. The following are true about cones: 
a. they are taller and thinner in fovea 
b. they are absent in the optic disc

c. 90% of the cones in the retina is situated outside 
    the central 5 degrees of the macula

d. the red and green pigments are encoded on the 
    long arm of X chromosome

e. the chromophore of each cone pigment exists as 

2. Myelin of the nerves is produced by:

a. fibroblast

b. macrophage

c. Schwann cell

d. oligodendrocyte

e. Müller cells

3. The following are true about human chromosomes:
a. chromosome 21 is bigger than chromosome 22

b. X chromosome is bigger than Y chromosome

c. the p arm of a chromosome is bigger than the q arm

d. acrocentric chromosome has very small short arm

e. 13q14 deletion means that band 13 on the long arm 
    of chromosome 14 is deleted.

. 4. The following antibiotics are useful for treating chlamydial
a. tetracycline

b. penicillin

c. sulphonamide

d. erythromycin

e. metronidazole

5. The retinal pigment epithelium:

a. contains both tight and gap junction

b. contains melanin on its apical surface

c. produces c wave of the ERG (electroretinogram)

d. produces part of the Bruch membrane

e. is not permeable to sodium fluorescein molecules

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