A patient presenting with severe mental retardation, seizures, ataxia and “puppet like gait” with a happy disposition prone to bouts of uncontrolled laughter is likely to have a defect in:
a) maternal chromosome 15q11-15q13
b) paternal chromosome 15q11-15q13
c) maternal chromosome 7p11-7p13
d) paternal chromosome 7p11-7p13
e) maternal chromosome 17q13-17q15
I think I can help with that!
The correct answer is (a) maternal chromosome 15q11-15q13.
The patient’s symptoms, including severe mental retardation, seizures, ataxia, “puppet-like gait”, and a happy disposition with uncontrolled laughter, are characteristic of Angelman syndrome.
Angelman syndrome is a genetic disorder caused by a deletion or mutation of the maternal copy of chromosome 15q11-15q13, which includes the UBE3A gene. This gene is normally imprinted, meaning that only the maternal copy is active.
The other options are not correct because:
– Paternal chromosome 15q11-15q13 (b) is associated with Prader-Willi syndrome, which has different symptoms.
– Maternal or paternal chromosome 7p11-7p13 (c and d) are not associated with this specific set of symptoms.
– Maternal chromosome 17q13-17q15 (e) is not associated with Angelman syndrome.
Note: Genetic imprinting plays a crucial role in Angelman syndrome, as the maternal copy of the UBE3A gene is the active one. If the paternal copy is inherited, it is normally silenced.