The probability that individual VI-1 would have this disease is: a. 1/4 b. 1/9 c. 1/18 d. 1/24 e. 1/36 f. 1/64 ODFOODOHO L11110 Solution Answer is option f. 1/64 .There are 6 generations and circle represents female whereas square represents male. The horizontal line between them represents mating whereas vertical line represents children/offspring. The double line represents consanguineous (related by blood) marriages. So the coloured squares/circles represents diseased/affected individuals. The diseased persons are found in the fourth generation and are offsprings of a consanguineous marriage. Since their parents are unaffected they are unaffected carriers, and the recurrence risk of the disease for each future child is 25%, while the risk of a child becoming a carrier like the parents is 50%. The fourth generation unaffected individuals will have probability of getting disease of 1/4. The fifth generation children mate with other individuals and will carry the risk of inheritance of disease probability as 1/4 x 1/4 = 1/16. Again in the fifth generation there is a consanguineous marriage and the VI 1 individual is found unaffected. So his probability of getting disease is 1/16 x 1/4 = 1/64.