In a family, the father has widely spaced eyes, increased facial hair and deafness. One of the three children has deafness with similar facial features. The mother is normal. Which one of the following is most likely pattern of inheritance in this case?
A i.e. Autosomal dominant (most likely) Waardenburg's Syndrome (WS) is a rare autosomal dominant syndrome characterized by pigmentary disturbances (skin, hair, iris), sensorineural hearing loss, and other developmental anomalies such as dystopia canthorum (widely spaced eyes) and blepharophimosis. The syndrome that closest matches the features provided in the question is Waardeburg syndrome type-I. This is inherited as an autosomal dominant fashion and hence is the answer of exclusion. As the question does not provide us with details as to the sex of the three children, a sex linked inheritance pattern cannot be worked out. Also the combined presentation of an affected father, unaffected mother and one affected child among three children is possible with both an autosomal dominant and an autosomal recessive inheritance pattern. In absence of any more details, the answer to this question cannot be deduced through the exploration of various permutations and combinations. How both autosomal dominant and autosomal recessive inheritance can be responsible for the above combination: Autosomal Dominant Autosomal recessive (A-affected allele and a normal allele) If the disease is transmitted in an Autosomal Dominant then :Father (affected) will be either 'AA' or 'Aa' Mother (unaffected) will be 'aa' If father is AA and mother aa, the offsprings will be 1. aA - 100% affected If father is Aa and mother aa, the offsprings will Aa - 50% affected aa - 50% not affected The scenario in the above question therefore is possible autosomal dominant inheritance if father is Aa and mother is aa (A'-affected allele and 'a' normal allele) If the disease is transmitted in an Autosomal recessive form :Father (affected) will be 'AA' Mother (unaffected) may be 'aa' or 'Aa' If father is AA and mother aa, the offsprings will be 1. aA - 100% not affected, (but carriers) If father is AA and mother Aa, the offsprings will be Aa - 50% not affected, carrier AA - 50% affected The scenario in the above question therefore is possible with autosomal recessive inheritance if father is aa and mother is Aa
Autosomal dominant
Autosomal recessive
X-linked dominant
X-linked recessive