Difference Between Inbreeding and Outbreeding

Main Difference – Inbreeding vs Outbreeding

Breeding refers to the mating and production of offspring by animals. Inbreeding and outbreeding are two methods of breeding, classified based on the relativity of the animals used in the breed. The main difference between inbreeding and outbreeding is that inbreeding is a breeding method that involves more closely-related individuals whereas outbreeding is a breeding method that involves unrelated animals. The main advantage of inbreeding is the development of pure lines by increasing homozygosity. However, hybrid organisms with desirable characteristics than both parents can be produced by outbreeding.

Key Areas Covered

1. What is Inbreeding
     – Definition, Facts, Advantages and Disadvantages
2. What is Outbreeding
     – Definition, Facts, Advantages and Disadvantages
3. What are the Similarities Between Inbreeding and Outbreeding
     – Outline of Common Features
4. What is the Difference Between Inbreeding and Outbreeding
     – Comparison of Key Differences

Key Terms: Backcross, Heterozygosity, Homozygosity, Hybrid, Inbreeding, Inbreeding Depression, Mating, Outbreeding, Self-breeding

Difference Between Inbreeding and Outbreeding - Comparison Summary

What is Inbreeding

Inbreeding refers to breeding from closely-related animals, especially over many generations. It increases the homozygosity of the offspring. Homozygosity refers to the state of possessing homozygous alleles. Hence, inbreeding can be used to maintain pure lines. Therefore, it is a technique used in selective breeding. Inbreeding naturally occurs in banded mongoose, bed bugs, common fruit fly, etc. In domestic animals, inbreeding is used to maintain desirable traits over many generations. The maintenance of homozygosity during inbreeding is shown in figure 1.

Main Difference - Inbreeding vs Outbreeding

Figure 1: Inbreeding

Selfing and backcross are two main types of interbreeding in addition to selective breeding. In selfing or self-breeding, both male and the female sex cells of the same organism fuse together. Backcross is the breeding of one individual of the offspring with one of its parents or with an organism that is genetically similar to the parent. Inbreeding increases the chance of offspring being affected by deleterious or recessive traits. This is the main disadvantage of inbreeding. A lot of genetic disorders such as hemophilia, sickle cell anemia, and cystic fibrosis are inherited as recessive traits. Inbred refers to an individual who inherits a deleterious trait from parents. Inbreeding depression is another disadvantage; this reduces the biological fitness of the population, reducing the ability of the offspring to survive and reproduce may occur.

What is Outbreeding

Outbreeding or outcrossing refers to a breeding method that involves unrelated organisms. As outbreeding combines the characteristics of different pure breeds, it increases the variation of a group of organisms through mating. The breeding of individuals in two populations of the same genus is an example of outbreeding. Outbreeding makes more heterozygous allele combinations within the offspring, randomly mixing all the possible alleles found in the population. Outbreeding depression is the main disadvantage of outbreeding in which the production of unsuitable traits for the present habitat is produced that reduces the fitness to the environment. Genetic variation of different human populations is shown in figure 2.

Difference Between Inbreeding and Outbreeding

Figure 2: Genetic Variation in Human Population

Interbreeding refers to the breeding involving individuals of different varieties of organisms that belong to the same genus. Some characteristics such as vigour of the offspring are hybrid in both outbreeding and interbreeding. Therefore, the offspring is referred to a hybrid. A hybrid has more beneficial traits than its either parent.

Similarities Between Inbreeding and Outbreeding

  • Inbreeding and outbreeding are two types of mating methods that produce offspring in animals.
  • Both inbreeding and outbreeding have their own advantages.

Difference Between Inbreeding and Outbreeding


Inbreeding: Inbreeding is the production of offspring from the breeding of organisms that are closely related genetically.

Outbreeding: Outbreeding is the production of offspring from the breeding of organisms that are genetically unrelated.

Type of Parents

Inbreeding: Closely-related organisms are used in inbreeding.

Outbreeding: Unrelated organisms are used in the outbreeding.

Common Ancestor

Inbreeding: Parents used for inbreeding are the same breed for 4-6 generations.

Outbreeding: Parents used for outbreeding should not be the common ancestor for 4-6 generations.


Inbreeding: Mating occurs between individuals of the same species in inbreeding.

Outbreeding: Mating occurs between separate species, genera, breeds or varieties.

Genetic Similarity

Inbreeding: Inbreeding occurs between genetically similar organisms.

Outbreeding: Outbreeding occurs between genetically somewhat dissimilar organisms.


Inbreeding: Inbreeding typically reduces the vigour of the offspring.

Outbreeding: Outbreeding increase the vigour of the offspring.


Inbreeding: Inbreeding is used for the development of pure lines by increasing heterozygosity.

Outbreeding: Outbreeding is used for the production of hybrid species with desirable characteristics.


Inbreeding: Harmful recessive alleles may be exposed during inbreeding. Inbreeding also leads to loss of fertility and productivity.

Outbreeding: The success rate of mating is less in outbreeding. Fertility of the offspring may be lost during outbreeding.


Inbreeding: Selective breeding, self-breeding, and backcross are examples of inbreeding.

Outbreeding: The breeding of individuals in two populations of the same genus is an example of outbreeding.


Inbreeding and outbreeding are two mating methods used for the generation of different advantageous animal breeds. Inbreeding is the mating of more related organisms while outbreeding is the mating of unrelated organisms. Therefore, the main difference between inbreeding and outbreeding is the genetic relationship between the parents.


1.“Inbreeding: Definition and Effects.” Study.com, .
2.“Outbreeding.” Genetics-Notes, .

Image Courtesy:

1. “Shetland pony inbred” By en:User:ImaginaryFriend – en:File:Shetland pony inbred.JPG (Public Domain) via
2. “Genetic Variation” By Jthiele at English Wikipedia via

About the Author: Lakna

Lakna, a graduate in Molecular Biology & Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things

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