If an organism expresses a recessive phenotype can you tell the genotype? Explain, include one example in your response.

Yes, if an organism expresses a recessive phenotype, we can make a prediction about its genotype. To understand why, let's first define some terms.

Genotype refers to the genetic makeup of an organism, specifically the combination of alleles it possesses for a particular gene. An allele is a variant form of a gene that determines a characteristic or trait. In diploid organisms, individuals have two copies of each gene, one inherited from each parent.

Phenotype, on the other hand, refers to the observable traits or characteristics of an organism, which can be influenced by both genetic and environmental factors.

When a recessive phenotype is expressed, it means that the individual shows a trait that is only observed when both copies of a gene are carrying the recessive allele. In this case, we can conclude that the genotype must be homozygous recessive (two copies of the recessive allele), as the presence of even a single dominant allele would result in a different phenotype.

Let's consider an example using the eye color trait in humans. The gene responsible for eye color has multiple alleles, but for simplicity, let's assume a simplified scenario with two alleles:

- Brown eye color allele (B) - dominant
- Blue eye color allele (b) - recessive

If an organism expresses the recessive phenotype of having blue eyes, we can infer that its genotype must be homozygous recessive (bb). This is because the presence of the dominant allele (B) would result in the dominant phenotype of brown eyes.

Therefore, in summary, if an organism expresses a recessive phenotype, it allows us to predict and conclude that the organism's genotype must be homozygous recessive for that particular trait.