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The Testcross: One Character (Mendelian Genetics)

Hi, thanks for watching my video about Testcross Tall plants produced in the F2 generation are predicted to have either the DD or the Dd genotype. You might ask if there is a way to distinguish the genotype. Mendel devised a rather simple method that is still used today to discover the genotype of plants and animals: the testcross. The organism expressing the dominant phenotype but having an unknown genotype is crossed with a known homozygous recessive individual. If a tall plant of genotype DD is testcrossed with a dwarf plant, which must have the dd genotype, all offspring will be tall phenotypically and Dd genotypically. If a tall plant is Dd and is crossed with a dwarf plant (dd), then one-half of the offspring will be tall (Dd) and the other half will be dwarf (dd). Therefore, a 1:1 tall/dwarf ratio demonstrates the heterozygous nature of the tall plant of unknown genotype. The results of the testcross reinforced Mendel’s conclusion that separate unit factors control traits. #testcrossgenetics #testcrossandbackcross