In this chapter, we focused on the Mendelian postulates, probabil...

Question

In this chapter, we focused on the Mendelian postulates, probability, and pedigree analysis. We also considered some of the methods and reasoning by which these ideas, concepts, and techniques were developed. On the basis of these discussions, what answers would you propose to the following questions:

How do we know whether an organism expressing a dominant trait is homozygous or heterozygous?

Accepted Answer

Hi, everyone. Let's take a look at this practice problem together, we have a blank trait can be masked by the blank trait if the organism is heterozygous. So we are looking at trait descriptions for a heterozygous organism and one type of trait will mask the other. Now, recall that heterozygous means having two different allys for any gene that we are referring to. So different allys also recall that allys can also be either dominant or recessive, having reviewed all that. Let's take a look at our answer choices and we're gonna go ahead and take a look at option C first C A dominant trait can be masked by the dominant trait. If the organism is heterozygous, this doesn't make sense as both traits are the same and one trait is not masking the other. So we can eliminate option C. Now let's take a look at option D A recessive trait can be masked by the recessive trait if the organism is heterozygous, this also doesn't make sense as they are both the same and one trait is not masked by the other. Therefore, we can eliminate option D as well. If we take a look at option A, we have a dominant trait can be masked by the recessive trait if the organism is heterozygous. Now, this is actually the opposite of what we want because we know that a dominant trait will be observable over a recessive trait. Therefore, A is incorrect as well. Lastly, we have option B A recessive trait can be masked by the dominant trait if the organism is heterozygous. This is the correct answer as it correctly describes the relationship between a dominant and a recessive trait in a heterozygous organism. All right, everyone. I hope you found this helpful and I'll see you for the next practice problem.

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