Question

With respect to typical Mendelian inheritance, which of the following statements is true for a cross between a tall plant with yellow seeds (TtYy) and a dwarf plant with green seeds (ttyy)?

• A. Tall plants with yellow seeds and dwarf plants with green seeds are produced in equal proportion.
• B. Both genotypic as well as phenotypic ratios obtained are same i.e. 1 : 1 : 1 : 1.
• C. This cites an example of a test cross which is performed to identify the genotype of an unknown parent.
• D. All of the above.

Answer 1

The correct option is D All of the above.

In a cross between a tall plant with yellow seeds and a dwarf plant with green seeds, the offsprings produced are: Tall plant yellow seed - TtYy = 4; Tall plant green seed - Ttyy = 4; Dwarf plant yellow seed - ttYy = 4; Dwarf plant green seed - ttyy = 4. Hence both genotypic as well as phenotypic ratios obtained are same i.e. 1 : 1 : 1 : 1. Tall plants with yellow seeds and dwarf plants with green seeds are produced in equal proportion. Test crosses are used to test an individual's genotype by crossing it with an individual of a known genotype. Individuals that show the recessive phenotype are known to have a homozygous recessive genotype. Individuals that show the dominant phenotype, however, may either be homozygous dominant or heterozygous. The phenotypically dominant organism is the individual in question in a test cross. The purpose of a test cross is to determine if this individual is homozygous dominant or heterozygous.