AGB 121: Principles of Animal Genetics and Population Genetics (2+1)

BACK CROSS AND TEST CROSS

Back cross

• Back cross is a cross between F 1 hybrid and one of its homozygous parents .

Example

Test Cross

• Test cross is crossing of an incompletely known genotype to a genotype which is homozygous, recessive at all the loci under consideration.
• Test cross help to differentiate whether the individual is homozygous dominant or heterozygous.
• If the tested individual is heterozygous and the pairs of factors are segregating and assorting independently then the following phenotypic ratio will be obtained.
  • Mono hybrid test cross – 1 : 1
  • Di-hybrid test cross - 1 : 1 : 1 : 1
  • Tri-hybrid test cross - 1 : 1 : 1 : 1 : 1 : 1 : 1 : 1