Question

Consider the information given below about a family and answer the questions that follow.

Rafiq, a ten year old boy, injured himself badly during the games period in school. He was rushed to a nearby hospital as the bleeding could not be stopped despite the first aid given to him. His uncle had lost his life in a similar condition. Rafiq's entire family underwent a genetic analysis to detect Bleeder's disease. His parents, sister Farah and paternal grandmother were tested to detect the disease. Rafiq's mother and grandmother were found to be carriers of the Bleeder's disease.

1. Draw a single pedigree chart to show the pattern of inheritance in Rafiq’s family.
2. What kind of inheritance pattern prevails in Rafiq’s family?
3. What are the chances of
   1. Farah suffering from the same disease?
   2. Farah being a carrier of the same disease?

Answer 1

1. 
   
2. The inheritance pattern in Rafiq’s family is X-linked recessive.
   This type of disorder mainly affects males because they have only one X chromosome. Females usually act as carriers and do not show the disease. The presence of affected males and carrier females in the family confirms this pattern.
3. 
   
   1. Farah’s Genotype Possibilities: Farah is female (XX), so she needs to be Xhyh to have haemophilia.
       Mother: XhX (carrier).
      Father: XY (normal).
      Punnett Square:
      

      	Xh	X
      X	XhX	XX
      Y	XhY	XY

      Analysis:
      Farah can’t be XhXh because the father contributes X, not Xh. The chance of Farah suffering from haemophilia is 0%.
   2. Farah would be a carrier if she’s XhX (one normal allele, one haemophilia allele). 
      From the Punnett Square:
      Possible genotypes:
      XX (normal) = 50% chance.
      XhX (carrier) = 50% chance.
      There’s a 50% chance that Farah inherits the Xh trait from her mother and the X trait from her father, making her a carrier.