Single Gene Inheritance

Question 1

Dyschondrosteosis

Answer 1

• example of pseudoautosomal inheritance disorder
• manifested by skeletal abnormalities with disproportionate short stature and deformity of forearm
• caused by mutation of SHOX gene (present in pseudoautosomal region of Xp and Yp) that codes for TF
• possibility of X-linked male to male transmission

Question 2

Prader-Willi Syndrome (PWS)

Answer 2

-the difference is phenotypic expression observed in PWS and AS, based on parental origin, is a result of “Genomic Imprinting”
-identical mutation (deletion) as AS but different phenotypic abnormalities
-deletion in long arm of chromosome 15 (15q11-q13)
-if the defective chromo is inherited from father (deletion in paternal chromo 15) then its PWS
-obesity, excessive eating habit, small hands and feet, short stature and hypogonadism
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Question 3

Angelman Syndrome (AS)

Answer 3

• the difference is phenotypic expression observed in PWS and AS, based on parental origin, is a result of “Genomic Imprinting”
• identical mutation (deletion) as AS but different phenotypic abnormalities
• deletion in long arm of chromosome 15 (15q11-q13)
• if it is inherited from (deletion in maternal chromo 15) it is AS
• unusual facial appearance, short stature, severe intellectual disability and seizures