Understand the key terms: A 'genotype' refers to the genetic makeup of an organism, specifically the alleles it carries. An 'allele' is a variant form of a gene. A 'karyotype' is the complete set of chromosomes in a cell, often visualized to study chromosomal abnormalities. A 'phenotype' refers to the observable traits or characteristics of an organism, which result from the interaction of its genotype with the environment.