Understanding Dominance in Genetics: How Alleles Determine Trait Expression

the allele that is expressed if 1 or 2 are present in a genotype; ex. BB, or Bb

In genetics, alleles are different versions of a gene that can be present at a specific location, or locus, on a chromosome

In genetics, alleles are different versions of a gene that can be present at a specific location, or locus, on a chromosome. In this case, you are referring to a scenario where there are two possible alleles present in a genotype, and we need to determine which allele will be expressed.

The term used to describe how alleles are expressed is known as dominance. Dominance refers to the relationship between two alleles at a given locus, where one allele masks or suppresses the expression of the other allele.

To understand dominance, we use uppercase letters to represent dominant alleles and lowercase letters to represent recessive alleles. For your example, let’s use the letter B to represent the allele that is expressed if one or two are present in a genotype.

If we have a genotype of BB, both alleles present are the same (dominant), and therefore, the dominant allele will be expressed. In this case, the individual would exhibit the trait or characteristic associated with the dominant allele.

Similarly, if we have a genotype of Bb, again, there is at least one dominant allele present. In this scenario, the dominant allele would be expressed, and the individual will exhibit the trait associated with the dominant allele.

It is noteworthy to mention that for individuals with the genotype Bb, although they express the dominant allele, they still carry the recessive allele. This means that they can pass on the recessive allele to their offspring, even if they themselves do not show the recessive trait.

In summary, when one or two dominant alleles (BB or Bb) are present in a genotype, the dominant allele will be expressed, resulting in the manifestation of the trait associated with that allele.

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