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Parents: normal male (X^HY)    x      female carrier (X^HX^h)

Gametes:    X^H               Y                          X^H                X^h

F1:         X^HX^H            X^HX^h               X^HY               X^hY                                                        

     Normal woman  Carrier woman    Normal man    Hemophiliac man

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Female X^hX (carrier, since the father was hemophiliac X^hY), Male X^HY

a) What is the probability that they will have a hemophilic male child?

50% of male children will be hemophiliac.

b) What is the probability that they will have a hemophilic daughter?

None. The daughters will be healthy, half carriers.

c) What is the genotype of the offspring?

25% X^hX^H, 25% X^hY, 25% X^HX^H , 25% X^HY

d) How is this disease transmitted?

It is a disease linked to sex, specifically to the X chromosome.

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Normal woman but carrier    (X^hX^H)          x          hemophilic man (X^hY)

Gametes:                       X ^h       X ^H                                  X ^h        Y

Women: 50% normal carriers and 50% hemophiliacs.

Men: 50% normal and 50% hemophiliacs.

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Woman: X^hX^H because her father was hemophiliac (X^hY) and transmitted X ^h to her.

Crossing:            X^hX^H               x            X^HY

Gametes           X^h    X^H           x           X^HY

F1:             X^hX^H       X^hY           X^HX ^H      X^H Y

The probability of a hemophilic male child being born is 1/4 = 25%.

The probability that a hemophiliac girl will be born is 0%.

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Carrier woman Non-hemophilic man

P                         X^HX^h        x       X^HY

Gametes:       X^H      X^h              X^H      Y     

F1:            X^HX^H           X^HX^h            X^HY           X^hY        

      Normal woman Carrier woman Normal man Hemophiliac man

50% of male children will be hemophiliacs.

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As the offspring are only made up of hemophilia-bearing women (X^HX^h) and healthy men (X^HY), the father will have to have the Y and X^h chromosomes, so the father has to be hemophilic ( X^hY).

The mother must be a healthy non-carrier woman (X^HX^H)

P                     X^hY         x             X^HX^H

Gametes      X^h       Y                      X^H

F1                     X^HX^h          X^HY

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a)

Grandfather         X^hY (hemophiliac)

P                  X^HX^h (carrier)   x      X^HY (normal)

Gametes:       X ^H          X ^h              X^H          Y     

F1:             X^HX^H         X^HX^h              X^HY            X^hY        

      Normal woman Carrier woman Normal man Hemophiliac man

b) 50% of male children will be hemophiliacs.

c) No daughter will be hemophiliac, even if 50% of the daughters are carriers.

d) Hemophilia is determined by an X-linked recessive gene.

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Since hemophilia is caused by a recessive gene linked to the X chromosome (X^h), and neither parent has the disease, the father must be healthy and the mother a carrier. 

P                    X^HY           x              X^HX^h

Gametes       X^H        Y             X ^H          X ^h

F1               X^HX^H       X^HX^h          X^HY        X^hY

The daughter's genotype must be X^HX^H or X^HX^h. Healthy, although it can be a carrier of the disease.

The genotype of the children must be X^HY or X^hY, so 50% of male children will be hemophiliacs.