Primer in Genetics and Genomics, Article 5-Further Defining the Concepts of Genotype and Phenotype and Exploring Genotype-Phenotype Associations

Abstract

As nurses begin to incorporate genetic and genomic sciences into clinical practice, education, and research, it is essential that they have a working knowledge of the terms foundational to the science. The first article in this primer series provided brief definitions of the basic terms (e.g., genetics and genomics) and introduced the concept of phenotype during the discussion of Mendelian inheritance. These terms, however, are inconsistently used in publications and conversations, and the linkage between genotype and phenotype requires clarification. The goal of this fifth article in the series is to elucidate these terms, provide an overview of the research methods used to determine genotype-phenotype associations, and discuss their significance to nursing through examples from the current nursing literature.

Keywords: genomics; genotype; nursing research; phenotype; symptom science.

Figure 1.

Locus, alleles, and genotype example. In this hypothetical chromosome pair, the colored bands indicate the specific locus. The letters labeling these bands (A and T) indicate different nucleotides present in the alleles at that locus, illustrating an “AT” genotype. A = adenine; T = thymine.

Figure 2.

Example path for the discovery of genotype–phenotype associations when there are no currently known genotypic associations for a particular phenotype.

Figure 3.

Genome-wide association study (GWAS) results plot. This sample plot identifies the results of a GWAS analysis. Data resulting from microarray analyses are visualized on a plot with genomic position on the horizontal scale and the level of association between the reference genes and the participants’ samples on the vertical scale. The dotted horizontal reference line indicates the threshold level of statistical significance of the association. In this example, five loci met the significance threshold. Image was obtained from the Creative Commons and was downloaded from Wikimedia Commons on January 4, 2017 (https://commons.wikimedia.org/wiki/File:Manhattan_Plot.png). Original source for image: Ikram et al. (2010).