Question

Hemophilia is a sex linked trait. Mary's father has hemophilia, but she does not. She marries a man who does not have hemophilia. What are the chances that she has a son with hemophilia? Make a punnett square to prove your answer!

Answer 1

If Mary does not have hemophilia, she must be a carrier of the mutated gene. Since her husband does not have hemophilia, their chances of having a son with hemophilia are 0%. This can be illustrated using a Punnett square.

Step-by-step explanation:

Hemophilia is an X-linked recessive disorder, meaning it is inherited on the X chromosome. Since Mary does not have hemophilia, she must have received a normal X chromosome from her mother. However, since her father has hemophilia, he must have passed on the mutated X chromosome to Mary. When Mary marries a man who does not have hemophilia, he would have a normal X chromosome to pass on to their children. Therefore, the chances of Mary having a son with hemophilia are 0%, as he would need to inherit the mutated X chromosome from both parents.

To illustrate this, let's create a Punnett square:

Mary's Genotype: XhX

Man's Genotype: XNY

Possible Gametes for Mary: Xh

Possible Gametes for Man: XN or Y

The Punnett square would show that all possible offspring would have a normal X chromosome, XN, and therefore, no son can have hemophilia.

Answer 2

Mary is a carrier of hemophilia, and thus she has a 50 percent chance of having a son with hemophilia, because male offspring inherit only one X chromosome which could carry the defective gene.

Step-by-step explanation:

Understanding Hemophilia and X-linked Recessive Inheritance

Hemophilia is a sex-linked trait that predominantly affects males due to its X-linked recessive inheritance pattern. Females typically need two mutated X chromosomes to express hemophilia but carrying one mutated X chromosome makes them carriers. Mary's father has hemophilia, indicating that she has one X chromosome with the hemophilia gene (since her father must have passed it on) and one normal X chromosome (as she does not express the disease).

Considering Mary marries a man who does not have hemophilia, we can deduce that he has a normal X and Y chromosome. Using a Punnett square, we symbolize Mary as XhX and her husband as XY. The Punnett square would look like this:

• 
  
• Xh X
• 
  
• X Y

The possible genetic combinations for their children would be:

• 
  
• XhX (carrier daughter)
• 
  
• XX (non-carrier daughter)
• 
  
• XhY (hemophilic son)
• 
  
• XY (non-hemophilic son)

The sons have a 50 percent chance of being affected by hemophilia. The daughters could be carriers like their mother but will not have the disease because they would receive at least one normal X chromosome from their father.