Identify the correct statements about test cross.
(A). It can predict the genotype of the test organism
(B). It can distinguish homozygous and heterozygous among test organisms
(C). It is another name for back cross
(D). It is the law of dominance
Choose the correct answer from the options given below.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A) and (B) only
(A) It can predict the genotype of the test organism Correct. The recessive parent (tt) gives only recessive (t) gametes. So the progeny show which alleles the test plant carries.
(B) It can distinguish homozygous and heterozygous among test organisms Correct. A tall plant may be TT or Tt; it looks the same either way. The test cross tells them apart:
TT × tt → all Tt, all tall: the test plant is homozygous.
Tt × tt → 1 Tt : 1 tt, half tall and half dwarf: the test plant is heterozygous.
(C) It is another name for back cross Incorrect. A back cross is a cross of the F1 with either of its parents. A test cross is a back cross with the recessive parent only. So every test cross is a back cross, but a back cross with the dominant parent is not a test cross. The two names do not mean the same thing.
(D) It is the law of dominance Incorrect. The law of dominance is one of Mendel’s laws. It says that in a heterozygote only the dominant factor shows itself. A test cross is a method of finding a genotype, not a law.
NCERT Extract:
Inheritance of One Gene – …
