Inbreeding : Definition, Examples, Types and Consequences

Inbreeding is the process of mating of genetically similar organisms. In humans, it is associated with endogamy and incest, in which sexual relations and children occur between close relatives. There are two types of inbreeding: Close inbreeding and line inbreeding. Inbreeding can cause a decline in survival and reproduction, known as inbreeding depression. In this article, we are going to discuss what inbreeding means, and what are the types of it, and we will also look at its advantages and disadvantages, and the Causes of Inbreeding.

Inbreeding Definition

Inbreeding is the mating of closely related individuals, such as siblings or cousins that results in a higher likelihood of expressing recessive genetic traits.

What is Inbreeding?

Inbreeding is the reproduction of offspring from mating or procreation between individuals genetically related to one another. By analogy, the term is used in human reproduction. Still, it more generally refers to genetic diorders and other consequences that can arise from the expression of harmful recessive traits as a result of incestuous sexual relations and incest. Animals rarely escape incest.

Inbreeding results in homozygosity, which may increase the likelihood of offspring being affected with recessive traits. Crossbreeding between populations sometimes has positive effects on fitness-related traits, but sometimes has negative effects known as outbreeding depression. However, increased homozygosity increases the probability of fixing beneficial alleles and also slightly decreases the probability of fixing deleterious alleles in the population.

Types of Inbreeding

Types of inbreeding are as follows:

Close Inbreeding

Here, the close and consanguineous mating of parents with offspring (first-degree relatives), as well as first brothers and sisters is chosen. It also includes second-degree relatives being mated, such as grandparents and their respective grandsons.

Line Inbreeding or linebreeding

It consists in mating of animals which are not so closely related yet have a common ancestor somewhere down the line. Take, for example, cousin grandparents to grand-children. Linebreeding is designed to purposely increase the relationship between offspring and a certain desirable ancestor. In short, the aim of linebreeding is to maintain a close relationship between individuals in the pedigree while at the same time keeping inbreeding as low as possible.

Backcrossing

Backcrossing is the mating of a hybrid or another such as its parents genetically, to produce offspring similar in genetic structure. It is applied widely in horticulture, animal breeding and gene knockout organism production. The backcrossed hybrids are sometimes denoted with the abbreviation BC. For example, an F1 hybrid derived from one of its parents (or a genetically identical individual) may be called a BC2. From the same individual, hybrid BC2 is produced by crossing BC1 hybrid.

Aslo Read: Mendel’s Laws of Inheritance

Selfing

Selfing inbreeding is a form of inbreeding that plants and organisms practise when they fertilize their own eggs with self-made pollen. It is as if the plant mates with itself. It is also known as self-fertilization. It ensures reproduction, but can reduce genetic diversity and makes the expression of harmful traits possible.

Examples of Inbreeding

Example of Inbreeding are as follows:

Human Inbreeding:

In the past, some royal families married their close relatives to maintain a special bloodline and remain powerful. Unfortunately, this produced health problems in some descendants of the royals who were children from parents too closely related.

Plant Inbreeding

Some crops, such as fruits and vegetables for seed breeding. This helps create new varieties. If we do this too much, then the crops would not have a good chance to mature and could easily become sick. We won’t be left with enough healthy fruits and vegetables.

Animal Inbreeding

When humans keep track and selectively breed animals, they are trying to make sure the babies inherit good attributes. This is useful in farming. But if we don’t do this carefully, animals will be unable to give birth; they may fall ill more easily. It’s like you have to ensure the animals carry all their best qualities, but without hurting them.

Advantages of Inbreeding

Advantages of inbredding are as follows:

1. Trait Fixation: Inbreeding may be useful to ensure that certain traits are fixed within a population.
2. Genetic Purity: This is a method which may conserve some of the genome.
3. Consistency in Traits: Consistency in expression of desirable traits enhances breeder’s ability to accurately anticipate characteristics of the progeny.
4. Economical: In most cases, inbreeding is less expensive because a few breeding individuals are required and therefore, there is a reduction of maintenance costs.
5. Rapid Progress in Trait Selection: The ability to achieve desired objectives quickly is another significant advantage associated with inbreeding as it allows breeders to fix certain traits rapidly.

Disadvantages of Inbreeding

Disadvantages of Inbreeding are as follows:

1. Increased Risk of Genetic Disorders: Expressing recessive inheritance disorder is more likely when inbreeding.
2. Reduced Fitness: Inbreeding offspring is highly likely to have a low level of overall fitness and low survival rates.
3. Loss of Genetic Diversity: While inbreeding reduces genetic variability across a population, leading to susceptibility to natural stressors and diseases.
4. Inbreeding Depression: Inbreeding depression is when the fitness of the population decreases as recessive deleterious alleles become expressed after continuous breeding.
5. Reduced Immunity: Inbred subjects are often weak as far as their immunity goes, which exposes them to diseases and infringements.
6. Decreased Fertility: Fertility of individuals that are born as a result of inbreeding, is greatly reduced affecting the success of a population at reproduction.
7. Cumulative Effect of Undesirable Traits: Inbreeding will lead to expression of the undesirable trait in cases where a specific population has it. The implications may be dire for such a population if this problem extends over generations.

Causes of Inbreeding

Causes of inbreeding are:

• Small Population Size: A small population size is one of the major causes of inbreeding. Individuals in smaller communities or isolated groups have lesser opportunity of obtaining a mate thus are likely to marry their relations.
• Geographic Isolation: Isolation can lead to inbreeding when populations are put apart by a physical barrier like a sea, valley, mountain range or desert. This isolation will restrict the gene pool as individuals within the groups are left with no other option apart from mating with their siblings or people within close proximity.
• Cultural Practices: Cultural practices or religious beliefs could restrict mate selection resulting into incidences of endogamy and therefore increase inbreeding.

Consequences of Inbreeding

Consequences of inbreeding are:

• Increased Expression of Deleterious Traits: The major result of inbreeding is that there comes into play of “deleterious” traits. Since harmful recessive genes are common in close relatives, they are likely to produce genetic diseases if reproduced among themselves.
• Loss of Genetic Diversity: Inbreeding is the process by which individuals breed with their close kin, leading to decreased genetic diversity at the species level. A species can only be adaptive and survive where there are genetic variations in the environment. Populations lacking diversity may experience increased susceptibility to diseases and environmental stressors.
• Reduced Fitness and Reproductive Success: Often, inbred individuals have poor fitness and reproductive success. These may be characterised by reduced fertility rate, high vulnerability to diseases and thus low fitness in the natural world.

Implications of Inbreeding

Implication of inbreeding are:

• Conservation Challenges: It presents problems that are more challenging than others in conservation, particularly on endangered species and their diminishing numbers. Breeding programs need to be well managed by conservationists to avoid consequences of inbreeding, and preservation of genetic variety.
• Human Health Considerations: Human societies normally do not permit any kind of in-breeding; however, it may happen especially among some tiny groups that live at a distance from each other. Therefore, this may increase risks of genetics problems and disease among these communities.
• Animal Husbandry: For instance, breed development programs cannot work well with regard to inbreeding especially when it comes to agriculture in livestock. Inbreeding, which is unregulated, may result in a decrease in farm output, exposure to more illnesses, as well as a degradation in the quality of cattle.

Conclusion – Inbreeding

Inbreeding is the mating of related individuals to produce offspring. It can be useful for retaining desirable characteristics and eliminating undesirable ones. However, it can also have negative effects. Inbreeding can cause more recessive genes to become homozygous, which means they have two identical alleles. This can increase the chances of offspring being affected by recessive traits. Breeding management, genetic testing and awareness on the need for diversity are some of the strategies applied towards mitigating the effects of inbreeding.

FAQs – Inbreeding

What is Inbreeding?

Inbreeding is breeding between closely related individuals such as siblings or cousins, which increases the chance for similar genetic material.

What are the Effects of Inbreeding?

Inbreeding may result in loss of genetic diversity leading to the expression of serious, inherited disorders; decreased reproductive success and overall ill-health.

Explain Inbreeding Depression.

Inbreeding depression results from the expression of harmful recessive alleles shared by both parents.

What are the Advantages of Inbreeding?

In a selective breeding program, inbreeding is one avenue to concentrate desirable traits and establish uniformity within the population.

Why does Continued Inbreeding Lead to Loss of Fertility and Vigour?

Inbreeding enhances the chances of carrying harmful mutations, which increases recessive expression and lowers fertility. The loss of genetic variety further diminishes vitality in general.