In genetics, what is an organism's phenotype?

• A. The complete set of DNA sequences present in an organism's genome
• B. A heritable change in gene expression that occurs without alteration of the DNA sequence
• C. The observable characteristics of an organism resulting from the interaction of its genotype and the environment
• D. The specific allelic makeup of an organism at one or more loci

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the term 'phenotype' in genetics. It refers to the observable traits or characteristics of an organism, such as height, eye color, or blood type.
2. Step 2: Recognize that phenotype results from the interaction between an organism's genotype (its genetic makeup) and environmental factors. This means that both genes and environment influence the traits you can observe.
3. Step 3: Differentiate phenotype from genotype. Genotype is the specific allelic composition of an organism, while phenotype is how those genes are expressed visibly or functionally.
4. Step 4: Note that phenotype is not the same as the complete DNA sequence (genome) or epigenetic changes (heritable changes in gene expression without DNA sequence alteration). These are related but distinct concepts.
5. Step 5: Conclude that the correct definition of phenotype is the observable characteristics of an organism resulting from the interaction of its genotype and the environment.