Test Cross vs. Backcross
Key Differences
Comparison Chart
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Classification
Breeding
Function
Test Cross and Backcross Definitions
Backcross
Backcross
Backcross
Backcross
Backcross
Backcross
Backcross
Backcross
Test Cross vs. Backcross
A test cross is used to differentiate the genotype of an individual which is phenotypically dominant whereas a backcross is using to recover a selecting genotype from a parent which allows the best genotype. A test cross is a cross that arises between a dominant phenotype and a recessive phenotype while the backcross is the cross that appears between a generation F1 hybrid and one of the two parents. All test crosses are backcrosses whereas backcross of an F1 hybrid with the recessive phenotype can reflect as a test cross. In testcross, the F1 hybrid is cross with recessive genotype whereas in backcross the F1 hybrid is cross with either homozygous dominant or heterozygous genotypes. Test cross-classifies the zygosity of the dominant phenotype whereas backcross recovers the best genotype.
What is a Test cross?
The breeding of a dominant phenotype with the recessive phenotype is denoting as a test cross. The proportion of the phenotypes in the progeny may determine the zygosity of the dominant phenotype. Zygosity is the degree of comparison of the dominant phenotype which examines during the test cross between two alleles which regulate a particular trait. The zygosity is identifying by the ratio of phenotypes arising in the offspring. It can make either homozygous or heterozygous. If an individual displays the dominant phenotype, the genotype of that actual individual is either homozygous dominant or heterozygous. Homozygous individuals comprise of either two dominant alleles or two recessive alleles. The heterozygous individuals include both dominant and recessive alleles of the gene. In this situation, the specific genotype can determine by performing a test cross with an individual displaying the recessive phenotype for that feature. The genotype of the recessive phenotype is continuously homozygous recessive for that particular trait.
In a test cross, the F1 hybrid is cross back with the recessive parent. Mendel is the first individual to make the test cross to identify whether an individual is heterozygous or homozygous for the dominant character. Other than discovering heterozygosity, test cross is also useful to form the purity of the gametes produces by parents. For examples, if a homozygous dominant F1 hybrid (TT) crosses with the recessive parent, it always results in 100% heterozygous tall hybrids. If a heterozygous dominant F1 hybrid (Tt) crosses with the recessive parent, only 50% is tall, and the rest 50% is dwarf.
What is Backcross?
In backcross, the F1 hybrid is cross back with any of the parent, either dominant or recessive. Backcrosses increase the useful traits in a population. When F1 is breeding with the homozygous dominant, the offspring produces a 100% dominant phenotype. When the F1 is breeding with a recessive phenotype, the offspring produces 50% dominant and 50% recessive phenotypes. This cross produces an offspring which is inherently same or closer to the parents of the F1. Hence, backcross is often using in horticulture and animal breeding to accomplish genetically identical offspring carrying the best genotypes.
The offspring of the F1 hybrid, backcross with the persistent parent is denotes as BC1 hybrid. The progeny of the BC1 hybrid, backcross with the repeated parent is referred to as BC2 hybrid. Through a backcross, a particular genotype can recovers if the persistent parent comprises of a selecting genotype.
For example, certain crop plant hybrids are backcross with wild species to improve their useful traits such as disease resistance, high yield, etc. However, this process may become weaken the other useful characters of hybrid. To overwhelmed this disadvantage, hybrids are backcross always with its parent plants over a few generations to obtain their good traits back into the new combinations.
