What characteristic is essential for a pure strain organism?

A pure strain organism is defined by its genetic uniformity, particularly in terms of its allele composition. This means that it is homozygous for the traits being considered, having identical alleles for those traits on both homologous chromosomes. This genetic consistency is crucial for maintaining the specific characteristics of the strain, allowing for reliable predictions in breeding and research.

In contrast, heterozygous traits would involve different alleles at a gene locus, resulting in variability that doesn't represent a pure strain. Hybrid traits arise from the crossing of two different strains or varieties, leading to offspring that may express a combination of traits rather than a consistent genetic make-up. Non-genetic traits, such as those influenced by environmental factors, do not pertain to the genetic uniformity required to be classified as a pure strain. Therefore, the essential characteristic for a pure strain organism is having homozygous traits, ensuring consistency and predictability in the traits expressed.