In addition, DR3/4 siblings who share both HLA haplotypes identical by descent with their diabetic DR3/4 sibling are at a higher risk than those sharing 1 or no haplotypes (13).
In the Diabetes Autoimmunity Study in the Young (DAISY) cohort, siblings of children with T1D who have HLA DR3/DR4-[DQB1.sup.*]0302 and are identical by descent for both HLA haplotypes with their diabetic proband sibling were observed to have a 65% risk for developing islet autoantibodies by age 7 years and a 50% risk of developing diabetes by age 10 years (13).
The COP measures the degree of genetic relatedness among genotypes based on pedigree information by estimating the probability that a random allele from one genotype is identical by descent
to a random allele of another genotype at the same locus (Kempthorne, 1969).
A co-ancestry (or kinship) coefficient is the probability that an allele randomly drawn from one individual is identical by descent
(autozygous) within the pedigree to an allele drawn from another individual and is equivalent in value to the inbreeding coefficient for these individuals' prospective offspring (Hartl and Clark 1989).
Therefore, Princess-77 and SWI-11 are 50% identical by descent
Haplotype identity between individuals who share a CFTR mutation allele "identical by descent
": demonstration of the usefulness of the haplotype-sharing concept for gene mapping in real populations.
F is the probability that the two alleles at the same locus in an individual are identical by descent
. In this paper, we assume that individuals mate randomly within populations, and therefore F is also the probability that any two alleles from the same locus chosen at random from a population are identical by descent
It is the probability that the two alleles at a locus are identical by descent
for a random plant in Cycle i.
A proportion, r, of the genes of cross-fertilizing relatives are identical by descent
from a common ancestor.
Coefficient of parentage (COP) (Kempthorne, 1969) indirectly measures genetic diversity among cultivars by estimating, from pedigree records, the probability that alleles at a locus are identical by descent
; however, assumptions made when calculating COP regarding relatedness of ancestors, selection pressure, and genetic drift are generally not met (Cox et al., 1985a, b; Graner et al., 1994; Kim and Ward, 1997).
Let us consider case 5 (for case 3 the same principles would apply but referring to gametes instead of to individuals) and assume that [[Chi].sub.t]([z.sub.t]) is the probability that two genes from two different males (females) in generation t are identical by descent
and y, the same probability for two genes, one each from a male and a female in generation t.
The coefficient of parentage (COP), which measures the probability of alleles in two individuals being identical by descent
, has been used extensively to indirectly assess diversity within germplasm pools.