Mutations on chromosome 17 are linked to which of the following neurodegenerative disorders?
C. A linkage to chromosome 17 has been shown for a specific variant of frontotemporal dementing syndrome. This syndrome is now referred to as frontotemporal dementia with parkinsonism-17 (FTDP-17). The linkage region contains the gene for tau protein. tau pathology is noted in various other dementing syndromes, including Alzheimer’s disease, where inappropriate hyperphosphorylation of tau is implicated in the production of neurofibril tangles.
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A 24-year-old man suffers from repeated episodes of sleepiness associated with sudden falls.
Which of the following polymorphisms is associated with this patient’s condition?
D. HLA stands for human leukocyte antigens. These molecules are expressed on the surface of white blood cells to coordinate the immune response. DR and DQ are two different types of HLA molecules. Many different HLA ‘subtypes’ (DR1, DR2, DQ1, DQB1*0602) exist normally. HLA DR2 subtype has been linked to narcolepsy–cataplexy syndrome. African-American narcoleptic patients are frequently DR2 negative but they have a stronger association with another HLA gene allele, HLA-DQB1*0602.
Which of the following genotypes has been shown to influence antisocial outcomes in maltreated children?
D. The gene for the MAO-A enzyme is located on chromosome X. In males a single X chromosome yields two dissimilar MAOA genotype variations: a high and a low activity variant. Females have two copies of the X chromosome, hence they can have three different levels of MAO-A activity: a high–high activity group (homozygous high), a low–low activity group (homozygous low), and a third, heterozygous group with low–high (mixed pattern). Caspi et al. (2002) studied MAO-A related genetic influences on the outcome of childhood maltreatment. They found out that high MAO-A activity exerts a protective influence against the development of antisocial outcomes (such as adolescent conduct disorder, violent episodes, etc.), especially in maltreated boys and to some extent in girls.
Which of the following features predicts a good response to lithium treatment in bipolar patients with acute mania?
D. Milder forms of mania respond better to lithium than severe mania. Patients with classical features of mania respond better than those with schizoaffective presentation. On a similar note, dysphoric mania, mixed affective episodes, and rapid-cycling mania respond poorly to lithium treatment. Having a family history of bipolar illness is suggestive of good prophylactic response of lithium in relapse prevention; such an effect is not clearly demonstrated for the effects of lithium in treating acute mania.
A 13-year-old boy presents with slow and clumsy walking and difficulties in writing. On examination he has a slurred speech with high stepping and a wide-based gait. Deep tendon reflexes are absent and plantar responses are extensor bilaterally.
Which of the following chromosomes is implicated in the aetiology?
E. Friedreich ataxia (FRDA1) is caused by mutation in the gene encoding a protein called frataxin. The locus of the frataxin gene has been mapped to chromosome 9q. The most common molecular abnormality that affects the site of this gene is a trinucleotide repeat expansion of the triplet codon GAA in intron 1 of the frataxin gene. Another locus for Fredreich’s ataxia has been mapped to chromosome 9p; it is called FRDA2.
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