Answer:
<em> a) There is a 25% chance that their next child will be Rh-.</em>
<em>b) There is a 3/8 chance for a Rh+ girl</em>
Explanation:
As we know from the question that Rh is a dominant gene. A person having only one allele for the gene will show its effect as it is the dominant character.
This means that for a person to lack the Rh factor, it shall not have any allele with the Rh factor.
To illustrate the result, lets draw a punnet square:
Rh+ Rh-
Rh+ Rh+/Rh+ Rh+/Rh-
Rh- Rh+/Rh- Rh-/Rh-
For the probability for it to be a girl, we know that there are 50-50 chances for the next baby to be a boy or a girl. The chance of being Rh+ are 75% for the next baby.
Hence,
3/4 multiplied by 1/2 is 3/8 ,which is the chance for the next baby to be a girl with Rh+ factor.
