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Backcross and test crossover

The backcrossing is the intersection between an individual and one of its parent (or a genotype identical to the parental). If the parent involved in the cross is the homozygous recessive (aa), it is called a test cross, since it serves to differentiate the homozygous individual (pure breed) from the heterozygous individual (hybrid, but with the same phenotype).

The test crossing consists, then, in crossing the dominant phenotype with the homozygous recessive one. If any of the offspring has a recessive phenotype, it will be because the parent was heterozygous (Aa), while if it is homozygous (AA) all the offspring will have the phenotype of the dominant one.

Questions that have come out in University entrance exams (Selectividad, EBAU, EvAU)

Aragon. June 2018, option B, question 3 .

Regarding Mendelian inheritance: (2.5 points)

b) If you had a vinegar fly ( Drosophila melanogaster ) with phenotype A, how would you check if it is AA or Aa? Reason for the answer (0.5 points)

Madrid, September 2017, option B, question 3

Regarding Mendel's contributions to the study of heredity: (2 points)

c) How is a backcross different from a test cross? (0.5 points).