Wednesday, 22 February 2017

(154) Coefficient of Inbreeding (C.O.I.)

Basic Dimension

http://sexualreligion.blogspot.com/ 


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http://abri.une.edu.au/online/pages/inbreeding_coefficient_help.htm

Explanation of inbreeding in animal populations relies on a few basic genetic principles. Genetic information is stored in ChromosomesChromosomes are made up of DNA. Genes are sections of DNA and occur in pairs. A particular gene will occur at a particular site (locus, plural is loci) in the DNA of a particular Chromosome. The different forms of a gene (usually 2) that can occur at that locus are called alleles. Where both alleles are the same at the locus, they are called homozygous. Where the alleles are different, they are called heterozygous. In general, the two alleles will have an equal influence on the performance of an animal. That is, the heterozygous form (both alleles are present) tends to have performance midway between the two homozygous forms. In a few cases, one allele will have the main (dominant) effect on an animal, while the other allele will only have an effect in its homozygous form. These are called dominant and recessive genes.






The coefficient of inbreeding (as proposed by Sewell Wright in 1922) is the probability that two alleles at a randomly chosen locus are identical by descent. Note that alleles may be identical for other reasons, but the inbreeding coefficient is just looking at the mathematical probability that the alleles have come from a common ancestor.







F (coefficient of inbreeding): F is the symbol for the coefficient of inbreeding, a way of gauging how close two people are genetically to one another. The coefficient of inbreeding, F, is the probability that a person with two identical genes received both genes from one ancestor.






https://www.youtube.com/watch?v=1H8mhSHCWxw









http://www.instituteofcaninebiology.org/blog/coi-faqs-understanding-the-coefficient-of-inbreeding


For comparison, mating of first cousins produces a COI of 6.25%; (in many societies this is considered incest and is forbidden by law). Mating of half-siblings produces a COI of 12.5%; mating of full siblings produces a COI of 25%.






Other strategy half siblings first cousins:









Other strategy first cousins:


Take, for example, the mating of first cousins who, by definition, share 
a set of grandparents. For any particular gene in the male, the chance
that his female first cousin inherited the same gene from the same source
is 1/8. [AB x (BC or BD)=.5^3]. Further, for any gene the man passes to his child,
the chance is 1/8 that the woman has the same gene and ½ that she transmits 
that gene to the child so 1/8 x ½ = 1/16. Thus, a first-cousin marriage has a 
coefficient of inbreeding F =1/16= 6.25%.




http://www.instituteofcaninebiology.org/blog/coi-faqs-understanding-the-coefficient-of-inbreeding


For comparison, mating of first cousins produces a COI of 6.25%; (in many societies this is considered incest and is forbidden by law). Mating of half-siblings produces a COI of 12.5%; mating of full siblings produces a COI of 25%.












The inbreeding coefficient for second cousins is 1/64: and for third cousins it is 1/256; 
1/64= .5^6=.0156; 1/64=.0156.








What about other COI examples?
Parent/offspring:  25%
Full sibling:  25%
Grandparent/grandchild:  12.5%
Half sibling:  12.5%
Great grandparents/great grandchild:  6.25%
First cousin:  6.25%












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