from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun A cross between an individual exhibiting the dominant phenotype of a trait and an individual that is homozygous recessive for that trait in order to determine the genotype of the dominant individual.
  • transitive verb To subject to a testcross.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun a cross between an organism whose genotype for a certain trait is unknown and an organism that is homozygous recessive for that trait so the unknown genotype can be determined from that of the offspring


Sorry, no etymologies found.


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  • If the mystery mutant and the known mutant sit on different chromosomes or a long way from each other on the same chromosome the grandkids of your ‘testcross’ will have an even mix of either one of the mutations, both or neither.

    Balloon Juice » 2006 » March 2006


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