Question

In 1952, an article in the British Medical Journal reported interesting differences in the behavior of blood plasma obtained from several individuals who suffered from X-linked recessive hemophilia. When mixed together, the cell-free blood plasma from certain combinations of individuals could form clots in the test tube. For example, the following table shows whether (+) or not (-) clots could form in various combinations of plasma from four individuals with hemophilia:

            1 and 1            -                                               2 and 3            +

            1 and 2            -                                               2 and 4            +

            1 and 3            +                                              3 and 3            -

            1 and 4            +                                              3 and 4            -

            2 and 2            -                                               4 and 4            -

What do these data tell you about the inheritance of hemophilia in these individuals?

Answer 1

The result suggest that two x linked genes cause hemophilia when mutant. Individuals 1 & 2 are mutant in one gene ( call it gene A) and individuals 3 & 4 are mutant in the other gene ( gene B) .