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Question 1 Short Answered Questions – (20%) Below is an imag…

Question 1 Short Answered Questions – (20%) Below is an image from G-banding analysis of a sample from a leukaemia patient. Abnormalities have been indicated by arrows.                             1a) Using ISCN nomenclature, what is the karyotype of this individual? (2 marks) — Below is an image generated by fluorescence in situ hybridisation (FISH) for Patient A, who is a newborn child displaying low birth weight, microcephaly, poor lung function, and a weak cry. The probes map to the q arm of chr12 (green) and the p arm of chr18 (red).                         1b) What genetic abnormality is present in Patient A, and what diagnosis would be made? (2 marks) — Below is an image generated by fluorescence in situ hybridisation (FISH). The probes map to 22q11.2 (red) and a control probe mapping to 22q13.3 (green).   1c) What genetic abnormality is present in the individual? (2 marks) 1d) The affected region is approximately 3 mb in size. Explain why FISH was used rather than G-banding for this patient. (4 marks) — ESSAY QUESTION – (80%) Critically evaluate G-banding, fluorescence in situ hybridisation (FISH) and CGH arrays for the detection of cytogenetic abnormalities. For each technique, explain how specific disorders could be diagnosed.

Question 2 Short Answered Questions – (20%) Below is the out…

Question 2 Short Answered Questions – (20%) Below is the output from analysis of the dystrophin (DMD) gene in a patient sample by multiplex ligation-dependent probe amplification (MLPA).   2a) What genetic abnormality has been identified in the patient sample? (2 marks) 2b) Why do MLPA probes contain a ‘stuffer’ sequence? (2 marks) 2c) The patient has no family history of muscular dystrophy. A blood sample from the patient’s mother was analysed and did not reveal any abnormality within the DMD gene. Explain the origins of the disease in the patient. (3 marks) 2d) A sample from a second patient revealed no insertions or deletions by MPLA. Explain why a diagnosis of Duchenne muscular dystrophy could not be excluded, and how diagnostic testing would proceed. (3 marks) — ESSAY QUESTION – 80% Explain the pathogenesis of the Duchenne and Becker muscular dystrophies. In your answer, critically evaluate exon skipping as a novel therapeutic approach for treating patients.