Color blindness is a defect in vision of colors, this defect is due to a localize-homologous segment of chromosome X.
In the document I have a pedigree which the parents and their children are normal; but then most of the children got married to a diseased one which 50% produced are diseased.
question: Is the allele responsible for color blindness dominant or recessive? Justify your answer.
The allele responsible for color blindness is recessive, but how do we justify?
Let N = normal allele and b = colorblind
Parents are XNY and XNXb
Only the girls in the first generation carried the b. If the boys had the b, they would be colorblind, because there would be no N on the Y chromosome.
To produce 50% colorblind, the males must have married colorblind females, so all of the male grandchildren would be colorblind and all of female grandchildren would be carriers.
Do a Punnett Square.
https://www.google.com/search?client=safari&rls=en&q=punnett+square&ie=UTF-8&oe=UTF-8&gws_rd=ssl
To determine whether the allele responsible for color blindness is dominant or recessive, we can analyze the pedigree provided. Here's how to justify that the allele is recessive:
1. Look for affected individuals: Identify the individuals in the pedigree who are color blind (diseased) and mark them as affected.
2. Observe the parents of affected individuals: Examine the parents of the affected individuals. If both parents are normal (not color blind), it suggests that the allele for color blindness is recessive because the affected individual inherited the color blindness allele from both parents.
3. Analyze the offspring of affected individuals: Look at the children of the affected individuals. If 50% of their children are color blind, it indicates that the parents are carriers of the color blindness allele but don't express the trait themselves. This pattern is consistent with a recessive trait because the color blindness allele needs to be inherited from both parents for an individual to be affected.
4. Determine the chance for unaffected children: If the allele were dominant, we would expect all children of affected individuals to be color blind. The fact that only 50% of them are affected suggests that the allele is recessive.
In conclusion, by examining the pedigree and observing that the parents of affected individuals are normal, and that 50% of the children of affected individuals are color blind, we can justify that the allele responsible for color blindness is recessive.