Test 211 (Recent MCQs)

1. The following are true about ocular histoplasmosis syndrome:

a. it is caused by Histoplasma capsulatum

b. a visit to a cave inhabited by bats is a significant history 

c. the patient is usually immunocompromised

d. pneumonia is usually present

e. the 'histo' test is positive in the majority of cases.

Answer
a.T   b.T   c.F   d.F   e.F
Ocular histoplasmosis syndrome is caused by the 
fungus Histoplasma capsulatum. This fungus enters
the body through the respiratory system as spores 
and may be acquired through the droppings of certain 
birds and bats. Unlike systemic histoplasmosis, the 
patient is not usually immunocompromised and pneumonia is rare. The 'histo' test does not distinguish between new infection and previous exposure but is present in 90% of patient with ocular histoplasmosis syndrome.

2. Regarding the human chromosomes:

a. there are 23 pairs autosomal chromosomes

b. the Y chromosome is larger than the X chromosome

c. cells containing YO chromosome are not compatible 
    with life

d. Barr body is caused by the presence of an inactive X 
    chromosome

e. Barr body is only found in people who are 
    phenotypically female

Answer
a.F   b.F   c.T   d.T   e.F
There are 23 pairs of chromosomes but only 22 paris 
are autosomal chromosomes. The Y chromosome is smaller than the X chromosome. YO cells are not compatible with life. Barr body is caused by the presence of an inactive X chromosome in a process 
known as Lyonization. It is found in cells which have 
more than one X chromosome. It can occur in 
phyenotypically males who have XXY chromosomes as in Klinefelter's syndrome.

3. The following are true about erythromycin:

a. it can be used to treat chlamydial infection effectively

b. it targets the cell wall synthesis of the bacteria

c. it decreases the renal excretion of cyclosporin

d. it causes cholestasis

e. it is ototoxic

Answer
a.T   b.F   c.T   d.T   e.F
Erythromycin targets the ribosomes of the bacteria.
It decreases the renal excretion of cyclosporin and
thus can be given concurrently with cyclosporin so
that less cyclosporin needs to be given. It can cause jaundice. Although erythromycin ends with -cin it is not a type of aminoglycosides which are ototoxic.

4. In autosomal recessive inheritance:

a. the rarer the trait the higher the possibility of marriages 
    within the same family

b. most recessive gene defects cause problem through 
    failure to produce functional protein

c. both males and females are affected equally severely

d. the chance of a child being affected if both parents are 
    carriers of a recessive gene is 50%

e. autosomal recessive retinitis pigmentosa is usually more 
    severe than autosomal dominant retinitis pigmentosa

Answer
a.T   b.T   c.T   d.F   e.T
Each parent has a 50% chance of transmitting the defective allele to a child. Since a child must
receive a defective allele from both parents to be affected, each child has a 25% chance of being affected.

5. Regarding the trochlear (fourth) nerve:

a. each trochlear nerve innervates the contralateral 
    superior oblique muscle

b. its nucleus is located above the cerebral aqueduct in 
    the midbrain

c. it enters the orbit through the circle of Zinn

d. it is a pure motor nerve

e. paralysis of the trochlear nerve is the most common 
    cause of vertical ocular misalignment.

Answer
a.T   b.F   c.F   d.T   e.T
The trochlear nerve decussates after leaving the midbrain. Thus, each trochlear nerve innervates the contralateral superior oblique muscle. Its nucleus is located below the cerebral aqueduct in the midbrain. It enters the 
orbit through the superior oblique fissure but outside the circle of Zinn. It is a pure motor nerve. Its paralysis is the most common cause of vertical ocular misalignment.
 

 

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