druas
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Physical exam of a 2 year old child with severe mental retardation shows a flat occiput,epicanthal folds and a flat nasal bridge.There is simian crease in both palms .chromosomes analysis shows 46 chromosomes.Which of the following types of genetic mutation is responsible for this condition?
A) Balanced translocation
B)Frame shift mutation
C)Microdeletion
D)Non disjunction
E)point mutation
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| robin082006
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Down Syndrome by balanced translocation
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| roopashri
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i would choose D
Downs pathogenesis is... meiotic nondisjunction(95%), robertsonian trnslocation(4%) , mosaicism(1%)
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| drk1980
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agree tht its a Translocation Downs...but whr is the choice for Unbalanced Translocation?
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| dariush
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A. it`s a Robertsonian Balanced Translocation (14:21) leading to Down.
--> GOOD TO KNOW THAT NOT ALL DOWN SYND ARE B/C OF TRISOMY 21 <--
"Balanced" means there is no extra pairs or missing copies. i.e. the total number of chromosomes are 46 unlike "Unbalaced"
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| drk1980
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can u explain this for me plz. Kaplan Cytogenetics chp talks, in 'balanced' translocation the offspring is either normal or a normal carrier. Its via an 'unbalanced' translocation that an offspring can develop the downs syndrome. The rest of the unbalanced products abort spontaneously. any idea abt this?
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| sturge_weber
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ya the ans should be unbalanced translocation
Roopashri, cant be d as the chr no. is 46, if chr were 47, then that choice
but since no choice matches, the closest is balanced translocation, though u re right drk1980. balanced will produce carriers...
whats the ans
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| roopashri
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thanks sturge, for correcting..
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