The Difference Between Test Cross and Back Cross
Breeding techniques are used in the field of genetics to analyze the inheritance of traits. Two such breeding techniques are Test Cross and Back Cross. While they may sound similar, they differ significantly in terms of their purpose, application, and results. In this article, we will explore the key differences between Test Cross and Back Cross.
Test Cross
Test Cross is a simple breeding technique that is used to determine if an organism exhibiting a dominant trait is purebred or heterozygous. It involves crossing an individual of unknown genotype with a homozygous recessive individual. If the offspring of the cross exhibit only the dominant trait, then the parent of the unknown genotype is purebred, and if the offspring exhibit both the dominant and recessive traits, then it is heterozygous.
For instance, let’s say an orchard owner wants to breed apple trees with smooth skin. He has a tree with a smooth surface, but he’s unsure if it’s purebred or heterozygous. He crosses it with a tree that has a wrinkled surface that is homozygous recessive. If all the offspring have smooth skin, the original tree is purebred for the smooth skin trait.
Back Cross
Back Cross, on the other hand, involves breeding between an individual with a dominant trait and its own offspring or a genetically similar individual or cultivar. This technique is used to reinforce or increase the frequency of a specific trait within a population.
For instance, a plant breeder growing tomatoes with large fruits may conduct backcrossing by crossing a tomato with large fruits with its offspring or a related cultivar to increase the frequency of the large fruit trait in the new generation.
Key Differences between Test Cross and Back Cross
– Purpose: The purpose of a test cross is to determine whether an individual with a dominant trait is purebred or heterozygous, while the purpose of a backcross is to reinforce or increase the frequency of a specific trait in a population.
– Breeders: Test crosses are primarily used by breeders to determine whether an individual is purebred or heterozygous, while backcrosses are conducted by breeders who want to strengthen or breed-in particular traits.
– Type of Cross: A test cross is a cross between an individual with a dominant trait and a homozygous recessive individual. A backcross, on the other hand, is a cross between an individual with a dominant trait and its offspring or a genetically similar individual or cultivar.
– Application: Test cross technique helps breeders identify purebred individuals, while the back cross technique increases the frequency of desirable traits such as disease resistance or yield.
In conclusion, Test Cross and Back Cross are both important breeding techniques used in genetics to understand and manipulate traits between generations of organisms. The key differences between Test Cross and back Cross are their purpose, breeders, type of cross, and application. Understanding the fundamental principals of these techniques is essential for any breeder looking to develop and cultivate new traits.
Table difference between a test cross and a back cross
| Test Cross | Back Cross |
|---|---|
| A cross between an individual with an unknown genotype and an individual with a homozygous recessive genotype to determine the unknown genotype | A cross between an individual with a heterozygous genotype and one of its homozygous parents to determine which alleles were inherited |
| Used to determine if an individual is homozygous or heterozygous for a particular trait | Used to determine which allele from one parent will be passed on to its offspring |
| Results in a 1:1 ratio of dominant to recessive phenotypes if the individual being tested is heterozygous | Results in a 1:1 ratio of the dominant and recessive phenotypes if the parent being backcrossed is heterozygous |