Question

Define and design a test-cross.

Answer 1

Previous Next. Answer:Crossing of F1 individual having dominant phenotype with its homozygous recessive parent is calledtest cross. The test cross is used to determine whether the individuals exhibiting dominant character are homozygous or heterozygous.

Answer 2

Dear Student,

◆ Test cross -

• Test cross is cross between individual with unknown genotype and an individual with a phenotypically recessive individual.
• It helps to determine zygosity (homozygous/heterozygous) of individuals showing dominant traits.

# Designing a test cross -

Let's take a cross between F1 hybrid of round and wrinkled seeds with homozygous plant with wrinkled seeds.

• Parents : F1 hybrid (Rr) × Homozygous recessive (rr)
• Gametes : R & r × r
• Progeny : Round seeds (Rr), Wrinkled seeds (rr)

Here, ratio of round seeds : wrinkled seeds is 1 : 1.

Hope this helps you...