Inbreeding occurs when related individuals mate and can increase the proportion of homozygosity. This raises the chances that offspring will be affected by recessive or deleterious traits, leading to genetic disorders and conditions. Inbreeding depression can result in smaller litters, lower fertility, and stillborn or deformed offspring in experiments with animals like adders. The inbreeding coefficient is used to measure inbreeding depression based on the expected and observed heterozygosity within a population. While inbreeding can establish desirable traits in livestock, it generally reduces survival and fertility over time.

1. Inbreeding
Definition : Inbreeding means mating between individuals that are related to each other
by ancestry (Falconer, quantitative genetics). It‘s very common in small population.
Impact :
Inbreeding increases the proportion of homozygosity which enhance the chances of
offspring being affected by recessive or deleterious traits.
It creates lot of genetic disorder like haemophilia, cysic fibrosis, sickle cell anemia
and so on
It is totally opposite to outbreeding.
Basically used in selective breedind like livestock – to eastablish new desirable trait in
the stock.
In livestock: Reduction of
Litter size and fertility.
Positive: Fastest racing dogs
Comes from homozygosity.
Common fruits female flies prefer mates with her own brothers.

2. Inbreeding in a diagram
www.iflscience.com/plants-and-animals/how-serious-inbreeding-show-dogs/
Affected by
deleterious allele

3. Inbreeding Depression
Experiment : Sweden
#Adders: 40 (Vipera berus).
Impact : Stillborn and deformed offspring
Fig : Vipera berus
http://evolution.berkeley.edu/evolibrary/article/conservation_03

4. Inbreeding Depression
Definition: The reduction of survival and fertility rate of inbred offspring.
 It occurs both plant and animal population as well as human .
 the harmful effect of inbreeding depression first observed by Charls Darwin, in 57 plant
species where self fertilization occurs between the individuals.
Inbreeding coeeficient
Definition: way of measurement of inbreeding depression.
Formula: F= (He – Ho) / He [if, inbreeding is only souce of diseuilibrium]
Here, F= Inbreeding coefficient,
He = Expected Heterozygosity, He = Observed Heterozygosity
Interpretation: F = 0 , no inbreeding
F= 1, complete inbreeding
Low F means less inbreeding
High F means significant inbreeding

5. Relationship between Kinship and inbreeding coefficient
Identity by State(ibs): if the two alleles are functionally same.
Identity by descent(ibd): Two alleles are ibd if one is direct physical copy of
other, or both of two are physical copies of the same ancestral allele.
Kinship coefficient (Φij ) : In between two individuals i and j, it is just probability
that one allele randomly selected from i and other allele is randomly selected
from the same autosomal locus of j, which are ibd.
Formula:
Here, k and l are the parents of individual i, f = inbreeding coefficient

6. References :
1. https://en.wikipedia.org/wiki/Inbreeding#/media/File:Fruit_flies.jpg
2. http://www.iflscience.com/plants-and-animals/how-serious-inbreeding-show-dogs/
3. http://evolution.berkeley.edu/evolibrary/article/conservation_03