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Q.
In order to find out the different types of gametes produced by a pea plant having the genotype AaBb, it should be crossed to a plant with the genotype
Scientists perform test cross to find out the different types of gametes or the genotype of an unknown individual. Test cross is performed always between the $F_{1}$ heterozygous plants and pure recessive (homozygous) parent plant. So, in the given case $AaBb$ should be crossed with $aabb$.