X-STR Linkage Group
Definition
A cluster of X-STR loci that are physically linked on the X chromosome and transmitted as a haplotype block in females. Loci within a group are not statistically independent; correct X-STR kinship statistics must account for within-group linkage.
- Location
- Loci physically clustered on the X chromosome
- Inheritance unit
- Transmitted together as a haplotype block in females
- Statistical effect
- Loci within a group are not independent
- Practical impact
- Kinship likelihood ratios must apply linkage correction
Common questions
Why does linkage matter for X-STR kinship calculations?+
Standard STR statistics assume each locus is inherited independently, but loci within one X-STR linkage group are co-transmitted as a block, so treating them as independent overstates a match's strength; kinship software must apply a linkage correction to avoid an inflated likelihood ratio.
Does linkage affect males and females equally?+
No. Males carry a single X chromosome so there is no within-generation recombination to consider, but females carry two X chromosomes and the linked loci pass down together across generations, which is where the co-inheritance and correction requirement arises.
How many linkage groups are typically recognised on the X chromosome?+
Commercial X-STR kits group their loci into a small number of linkage clusters, commonly four, based on physical position along the chromosome; loci in different clusters are far enough apart to be treated as effectively independent.
Related terms
- Argus X-12 QS
- Investigator Argus X-12 QS (Qiagen), the most widely validated commercial X-STR multiplex kit. Amplifies 12 loci in four linkage groups; used with...
- PowerPlex Y23
- Commercial Y-STR multiplex kit (Promega Corporation) amplifying 23 loci, overlapping substantially with Yfiler Plus. The 20-locus YHRD core set is covered by...
- Y-STR Haplotype
- The combination of allele values across all Y-chromosome STR loci typed in a single analysis. Reported as a string of allele values...
- Yfiler Plus
- Commercial Y-STR multiplex kit (ThermoFisher Scientific) amplifying 27 loci in a single PCR reaction. Current standard for Y-STR casework in many US,...
- YHRD
- Y-Chromosome STR Haplotype Reference Database, maintained at the Charité Berlin and freely accessible at yhrd.org. Contains over 340,000 haplotypes from 124 countries....