Which term describes an organism's expressed traits?

The term that describes an organism's expressed traits is "phenotype." The phenotype encompasses all of the observable characteristics or traits of an organism, including physical appearance, behavior, and physiological properties. These traits result from the interaction of the organism's genotype (the genetic makeup) with environmental factors.

In the context of genetics, while the genotype refers to the specific alleles present in an organism's DNA, the phenotype is the manifestation of those alleles. This distinction is crucial in fields such as genetics, evolutionary biology, and medicine, as understanding the relationship between genotype and phenotype allows researchers to predict traits and behaviors based on genetic information.

Other terms listed, like hemizygote, refer to a specific genetic situation where an organism has only one allele for a gene, often seen in males for X-linked traits. The karyotype involves the number and appearance of chromosomes in the nucleus, providing a blueprint of an organism's chromosomal makeup but does not directly convey the expressed traits. Hence, "phenotype" is the precise term that correctly describes the observable characteristics of an organism.