Final answer:
A term that is synonymous with "pure" or "true breeding" is homozygous, which describes an organism with two identical alleles for a trait. In genetics, this term is often associated with organisms that produce offspring with predictable traits.
Step-by-step explanation:
A term that has the same meaning as "pure" or "true breeding" is homozygous. This term refers to the genetic composition of an individual who has two identical alleles for a trait. In Mendel's experiments, purebred or true breeding plants were those that were homozygous for a specific trait, meaning they carried two of the same alleles at a gene locus. Such plants, when self-crossed or crossed with an identical homozygous plant, produce offspring that are genetically uniform and exhibit the same traits as the parent plants. These homozygous individuals will continue to pass on the trait reliably across generations without any variations.
When we talk about purebred animals, we are usually referring to the controlled breeding to produce offspring with specific and predictable traits. For example, a purebred or pedigree dog will have characteristics that conform to a specific breed standard due to selective breeding practices similar to what Mendel conducted with his pea plants. Similarly, in Mendel's genetic research, the purebred parents used in his experiments comprised the P1 generation.