Q. A diseased man marries a normal woman. They get three daughter and five sons. All the daughter were diseased and sons were normal. The gene of this disease is : -

 2448  218 AIPMTAIPMT 2002Principles of Inheritance and Variation Report Error

Solution:

Since the father is diseased and daughters also?die disease is not sex-limited of course, it is sex-linked. Sex linked inheritance may be X-linked as given in the question, Y-linked and XY-linked. In X-linked inheritance the characters are controlled by genes located on non homologous part of X-chromosome. These X-linked genes do not have their corresponding alleles on Y-chromosome. In daughter it is express even when present in heterozygous condition.