A family consist of husband, wife and 2 children. Wife's father has Huntington's chorea. Which statement is true: (AIIMS Nov 2009)
|A||Chance of getting disease in child is 1:4|
|B||Can occur up to age of 50|
|C||If the wife has the disease than the child will develop the disease at much early age.|
|D||Huntington's chorea is due to point mutation in gene.|
Can occur up to age of 50 & C . If wife does not get disease till age 50 children are not affected.
Huntington’s Disease: Inheritance and genetics:
1). It is inherited as an autosomal dominant disease
2). Genetic abnormality responsible for Huntington’s disease is a CAG trinucleotide expansion on a gene called 'Huntingtin' which is localized on chromosome 4.
3). Means age of onset HD: 40 – 50 years
Effect of parental sex in Huntington’s disease
Characteristic manifestations include
1). Gene inherited from father
2). Gene inherited from mother
1). Individuals who inherit the gene from their father usually have an early onset disease
2). Effect of Anticipation is exhibited strongly
3). ‘Anticipation' means that successive generations develop the disease at an earlier age than their parent.
4). When gene is inherited from father the phenomenon of Anticipation is exhibited strongly.
a. Individuals who inherit disease from the mother usually have a late onset disease
b. Effect of Anticipation is less characteristic
When gene is inherited from mother, the phenomenon of 'Anticipation' may be exhibited but this phenomenon is less marked or less characteristic.