Can you please help me with my biology hw? I don't understand how this works. 

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justaguide eNotes educator| Certified Educator

In part A, from the figure starting from P1, it is seen that the offspring of 2 individuals that do not have the phenotype attached earlobes have two daughters that have free earlobes, and only one of their sons has the attached earlobes. In F2, none of the individuals have the phenotype attached earlobe, and in F3 one individual has the phenotype.

This shows that the trait attached earlobe is recessive in nature. As a result an offspring of a pair with none having the trait can have the trait. This is seen in F3. Again, as seen in F2, though one of the parents has the trait none of the offspring has the same trait. Though it is evident that some of them are carriers as a person, F3 has the trait.

In part B, the tongue rolling trait is dominant. In P1, the mother is a carrier and exhibits the trait and the father does not carry the trait. In F1, two of the offspring are passed on a pair of the normal allele and two are passed on one copy of the mutant allele. This results in two of them having the trait. The person with the mutant allele marries a man that has only the normal allele but as the trait is dominant 2 of their 3 offspring in F2 have the trait. One of them that is not affected marries a person carrying the mutant allele. In F3, all their offspring have the trait.

In part C, the trait colorblind is dominant in males and recessive in females. In P1, the male is a carrier and shows the trait, the female is a person with normal color vision. In F1, their male offspring have normal color vision and at least one of their female children is a carrier. She marries a male that has normal vision, but the allele responsible for color blindness is passed on to one of their male children that is color blind. In F2, the affected male marries a woman that is a carrier of the trait. This results in one of their daughters being color blind. The mother of the color blind girl in F3 is a a carrier.

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