Topic Genetic Basis for Variation: Explain the terms ’true breeding plants’ and ‘test cross’.

Testcross – refers to breeding an organism of unknown genotype with a homozygous recessive individual. The phenotypic ratio of the offspring reveals the unknown genotype of the organism.

True breeding plants – refers to plants that produce offspring of the same variety (i.e. same heritable phenotype) when they self-pollinate. This is because its genotype is homozygous.

True breeding organisms can also be called pure-bred.  In the pure-bred Siamese cat, their ancestors were inbred until all the genes that produce the physical characteristics and temperament associated with the Siamese breed are homozygous.

Source: http://en.wikipedia.org/wiki/File:Siam_lilacpoint.jpg

How about reciprocal cross? Look out for it soon!