Question

प्रश्न-14 टेस्ट-क्रॉस को उचित उदाहरण सहित समझाइए।
Explain the Test-cross with suitable example.​

Answer 1

A test cross is used to find out the genotype of any plant with dominant expression when it is not known whether it is homozygous (pure) or heterozygous for that trait.

For example, a pea plant having purple flowers (F1 hybrid with unknown genotype) is crossed with a pea plant with white flowers (recessive).

Explanation:

• The test cross is an experiment first employed by Gregor Mendel, in his studies of the genetics of traits in pea plants.
• Mendel’s theory, which holds true today, was that each organism carried two copies of each trait.
• One was dominant trait, while one could be considered recessive.
• The dominant trait, if present, would determine the outward appearance of the organism, or the phenotype.

Answer 2

When it is unknown whether a plant with dominant expression is homozygous (pure) or heterozygous for that trait, a test cross is done to determine its genotype. For example, a purple-flowering pea plant (F1 hybrid of unknown genetics) is crossed with a white-flowering pea plant (recessive).