Question

How would you use a test cross to confirm that a plant with dominant morphology is truly homozygous dominant (TT)?

Options

• Observe the plant's phenotype across multiple generations without crossing

• Cross it with a heterozygous plant and observe a 3:1 ratio

• Cross it with another homozygous dominant plant and verify all offspring are TT

• Cross it with a homozygous recessive plant and verify that all offspring show only the dominant phenotype

Answer 1

To confirm a dominant phenotype plant is homozygous dominant (TT), perform a test cross with a homozygous recessive (tt) plant. If all offspring display the dominant phenotype exclusively with no recessive offspring, this confirms the parent was TT. Any appearance of recessive offspring would indicate heterozygosity.