Color blindness (B) is a recessive (b) sex-linked disorder that results from a mutation on the X chromosome. What would be the most likely phenotypes of the male and female progeny when a colorblind man and a woman with no family history of color blindness mate?
- All of the male and none of the female offspring will be colorblind
- Half of the male and half of the female offspring will be colorblind
- None of the male and none of the female offspring will be colorblind
- None of the male and all of the female offspring will be colorblind
Click for Explanation
This question asks the examinee to determine the offspring phenotypes that result from cross between a woman with normal vision and a colorblind man. To answer this question, the easiest method is requires the use of a Punnett square.
Since the woman has no family history of colorblindness, it is safe to assume that she is homozygous dominant (XBXB). The colorblind male on the other hand has the mutated allele (XbY).
According to the Punnett square above, none of the males and none of the females will be affected by this recessive disorder. Therefore, none of the male and none of the female offspring will be colorblind making C the correct answer.
Want more MCAT practice?
We’ve got options for every schedule and learning style!
From the best online MCAT course created by top instructors with 524+ MCAT scores to the most representative full-length practice exams and private tutoring, we can custom tailor your MCAT prep to your goals!
Not sure which option is right for you? Schedule a free MCAT consultation with an MCAT expert using the form below. No obligation, just expert advice.
