Linkage disequilibrium
Definition
The non-random association of alleles at different loci within a population. Certain HLA allele combinations (e.g., HLA-A1 with HLA-B8 with HLA-DR3) occur at higher frequency than expected by chance. Linkage disequilibrium must be accounted for when calculating combined haplotype frequencies in forensic statistics.
Related terms
- Absorption-elution
- A technique for detecting antigens on dried red cell debris. Specific antiserum is absorbed onto the stain; if the antigen is present,...
- Antiserum
- Serum collected from an immunised animal containing antibodies directed against a specific antigen or group of antigens. In species identification, antiserum raised...
- Blood group system
- A set of red cell surface antigens encoded by one gene locus or by two tightly linked loci. The International Society of...
- Complement-dependent cytotoxicity (CDC)
- A serological HLA typing method in which test lymphocytes are incubated with HLA-specific antibody and then with complement. If the antibody binds,...
- Conditional probability
- The probability of event A given that event B has already occurred, written P(A|B). Conditional probability is the basis of the multiplication...
- Hardy-Weinberg equilibrium
- A condition in a population where genotype frequencies at a single locus conform to expectations derived from allele frequencies alone, assuming random...
- HLA haplotype
- The specific combination of HLA alleles inherited as a block on one copy of chromosome 6. Because HLA loci are tightly linked,...
- HLA (human leukocyte antigen)
- Cell-surface glycoproteins encoded by the major histocompatibility complex (MHC) on chromosome 6p21. They present peptide antigens to T cells and are the...
- Multiplication rule
- For any two events: P(A and B) = P(A) x P(B|A). When A and B are independent, this simplifies to P(A) x...
- Paternity index (PI)
- A likelihood ratio that compares the probability of the observed serological profile if the alleged father is the biological father to the...
- Phenotype frequency
- The proportion of a given population that expresses a particular antigen combination. Multiplying phenotype frequencies across independent loci gives the combined frequency...
- Positive dependence
- Events are positively dependent when the occurrence of one increases the probability of the other: P(A|B) > P(A). In this case P(A...
Explained in these topics
- Conditional Probability and IndependenceA statistical association between alleles at different genetic loci in a population. If two loci are in linkage disequilibrium, allele combinations at those lo...
- The HLA System and Its Role in Forensic Relationship TestingThe non-random association of alleles at different loci within a population. Certain HLA allele combinations (e.g., HLA-A1 with HLA-B8 with HLA-DR3) occur at h...
- Minor Blood Group Systems: MNS, Kell, Duffy, and OthersA non-random association between alleles at different loci in a population. Within the MNS system, the M/N and S/s loci are physically close, so certain combin...