A sparse marker extension tree algorithm for selecting the best set of haplotype tagging single nucleotide polymorphisms

Ke Hao, Simin Liu, Tianhua Niu

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


Single nucleotide polymorphisms (SNPs) play a central role in the identification of susceptibility genes for common diseases. Recent empirical studies on human genome have revealed block-like structures, and each block contains a set of haplotype tagging SNPs (htSNPs) that capture a large fraction of the haplotype diversity. Herein, we present an innovative sparse marker extension tree (SMET) algorithm to select optimal htSNP set(s). SMET reduces the search space considerably (compared to full enumeration strategy), and therefore improves computing efficiency. We tested this algorithm on several datasets at three different genomic scales: (1) gene-wide (NOS3, CRP, IL6 PPARA, and TNF), (2) region-wide (a Whitehead Institute inflammatory bowel disease dataset and a UK Graves' disease dataset), and (3) chromosome-wide (chromosome 22) levels. SMET offers geneticists with greater flexibilities in SNP tagging than lossless methods with adjustable haplotype diversity coverage (Φ). In simulation studies, we found that (1) an initial sample size of 50 individuals (100 chromosomes) or more is needed for htSNP selection; (2) the SNP tagging strategy is considerably more efficient when the underlying block structure is taken into account; and (3) htSNP sets at 80-90% Φ are more cost-effective than the lossless sets in term of relative power, relative risk ratio estimation, and genotyping efforts. Our study suggests that the novel SMET algorithm is a valuable tool for association tests.

Original languageEnglish
Pages (from-to)336-352
Number of pages17
JournalGenetic Epidemiology
Issue number4
StatePublished - Dec 2005
Externally publishedYes


  • Association study
  • Entropy
  • Haplotype
  • Heterozygosity
  • Single nucleotide polymorphism
  • Tagging


Dive into the research topics of 'A sparse marker extension tree algorithm for selecting the best set of haplotype tagging single nucleotide polymorphisms'. Together they form a unique fingerprint.

Cite this