Understanding Recessive Alleles: The Role of Two Copies in Expression

the allele that is expressed only if 2 are present in the genotype; ex. bb

The allele that is expressed only if two copies are present in the genotype is called the recessive allele

The allele that is expressed only if two copies are present in the genotype is called the recessive allele. In this case, you mentioned the example of the genotype being “bb.”

In genetics, individuals have two copies of each gene: one inherited from their mother and one from their father. These copies are called alleles. Alleles can be either dominant or recessive.

In the case of the genotype “bb,” both copies of the gene are recessive alleles, indicating that there is no dominant allele present. Since the recessive allele does not exert its effect unless two copies are present, individuals with the genotype “bb” will show the trait associated with this allele.

This phenomenon is known as recessive inheritance. It means that in order for the trait controlled by the recessive allele to be expressed, both copies of the gene must be the recessive variant. If there is at least one dominant allele present, it will mask the effect of the recessive allele, and the trait associated with the dominant allele will be expressed.

This concept is important in understanding the inheritance of many genetic traits and diseases. For example, in human genetics, the recessive allele associated with the genetic disorder cystic fibrosis is only expressed when an individual has two copies of the recessive allele.

I hope this explanation clarifies the concept of a recessive allele and its expression when two copies are present in the genotype.

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