Until recently, the Y chromosome seemed to fulfil the role of juvenile delinquent among human chromosomes — rich in junk, poor in useful attributes, reluctant to socialize with its neighbours and with an inescapable tendency to degenerate. The availability of the near-complete chromosome sequence, plus many new polymorphisms, a highly resolved phylogeny and insights into its mutation processes, now provide new avenues for investigating human evolution. Y-chromosome research is growing up.

/pdf/the-human-y-chromosome-an-evolutionary-marker-comes-of-age-2nz5mvksa5.pdf

The human Y chromosome: an evolutionary marker comes of age

Sherlock Holmes said "it has long been an axiom of mine that the little things are infinitely the most important", but never imagined that such a little thing, the DNA molecule, could become perhaps the most powerful single tool in the multifaceted fight against crime. Twenty years after the development of DNA fingerprinting, forensic DNA analysis is key to the conviction or exoneration of suspects and the identification of victims of crimes, accidents and disasters, driving the development of innovative methods in molecular genetics, statistics and the use of massive intelligence databases.

/pdf/encoded-evidence-dna-in-forensic-analysis-3q4hcjdcbc.pdf

Encoded evidence: DNA in forensic analysis

DNA Commission of the International Society of Forensic Genetics (ISFG): an update of the recommendations on the use of Y-STRs in forensic analysis.

The freely accessible YHRD (Y Chromosome Haplotype Reference Database, www.yhrd.org) is designed to store Y chromosome haplotypes from global populations and had replaced three earlier database versions collecting European, Asian and US American Y chromosomes separately. The focus is to disseminate haplotype frequency data to forensic analysts, researchers, and to everyone who is interested in historical and family genetics. YHRD considers reduction of the available number of polymorphisms on the Y chromosome to a uniform data string of 11 highly variable Y-STR loci as an efficient way to rapidly screen many world populations and to make their Y chromosome profiles comparable. Typing of the YHRD 11-locus core set is facilitated by commercial products, namely diagnostic PCR kits, and endorsed by scientific and forensic analyst's societies as ISFG or SWGDAM. YHRD is structured by the assignment of each submitted population sample to a set of populations sharing a common linguistic, demographic, genetic or geographic background (metapopulations). This principle facilitates the statistical evaluation of haplotype matches due to a significant enlargement of sample sizes. With the rapid growth of the database the definition of homogeneous metapopulations is now also feasible solely on the basis of the genetic data as exemplified for the whole dataset of YHRD, release 19 (August 2006). Large sample numbers within genetically defined metapopulations also allows the development of biostatistical methods to estimate the frequency of unobserved or rare haplotypes ("haplotype frequency surveying method"). Essential for the YHRD project is its collaborative character relying on the engagement of individual laboratories to make their data accessible via YHRD and to share the YHRD standards regarding data quality.

Y chromosome haplotype reference database (YHRD): update.

Background: Accurate, high-throughput genotyping allows the fine characterization of genetic ancestry. Here we applied recently developed statistical and computational techniques to the question of African ancestry in African Americans by using data on more than 450,000 singlenucleotide polymorphisms (SNPs) genotyped in 94 Africans of diverse geographic origins included in the HGDP, as well as 136 African Americans and 38 European Americans participating in the Atherosclerotic Disease Vascular Function and Genetic Epidemiology (ADVANCE) study. To focus on African ancestry, we reduced the data to include only those genotypes in each African American determined statistically to be African in origin. Results: From cluster analysis, we found that all the African Americans are admixed in their African components of ancestry, with the majority contributions being from West and WestCentral Africa, and only modest variation in these African-ancestry proportions among individuals. Furthermore, by principal components analysis, we found little evidence of genetic structure within the African component of ancestry in African Americans. Conclusions: These results are consistent with historic mating patterns among African Americans that are largely uncorrelated to African ancestral origins, and they cast doubt on the general utility of mtDNA or Y-chromosome markers alone to delineate the full African ancestry of African Americans. Our results also indicate that the genetic architecture of African Americans is distinct from that of Africans, and that the greatest source of potential genetic stratification bias in casecontrol studies of African Americans derives from the proportion of European ancestry.

/pdf/characterizing-the-admixed-african-ancestry-of-african-3kqt5ut3j1.pdf

Characterizing the admixed African ancestry of African Americans.

To investigate geographic structure within U.S. ethnic populations, we analyzed 1705 haplotypes on the basis of 9 short tandem repeat (STR) loci on the Y-chromosome from 9-11 groups each of African-Americans, European-Americans, and Hispanics. There were no significant differences in the distribution of Y-STR haplotypes among African-American groups, whereas European-American and Hispanic groups did exhibit significant geographic heterogeneity. However, the significant heterogeneity resulted from one sample; removal of that sample in each case eliminated the significant heterogeneity. Multidimensional scaling analysis of R(ST) values indicated that African-American groups formed a distinct cluster, whereas there was some intermingling of European-American and Hispanic groups. MtDNA data exist for many of these same groups; estimates of the European-American genetic contribution to the African-American gene pool were 27.5%-33.6% for the Y-STR haplotypes and 9%-15.4% for the mtDNA types. The lack of significant geographic heterogeneity among Y-STR and mtDNA haplotypes in U.S ethnic groups means that forensic DNA databases do not need to be constructed for separate geographic regions of the U.S. Moreover, absence of significant geographic heterogeneity for these two loci means that regional variation in disease susceptibility within ethnic groups is more likely to reflect cultural/environmental factors, rather than any underlying genetic heterogeneity.

/pdf/y-chromosome-str-haplotypes-and-the-genetic-structure-of-u-s-1tqkc8t24a.pdf

Y Chromosome STR Haplotypes and the Genetic Structure of U.S. Populations of African, European, and Hispanic Ancestry

We describe here an online Y-chromosomal short tandem repeat haplotype reference database (YHRD) for U.S. populations, which represents 9-locus Y-STR haplotypes for 1705 African-Americans, European-Americans and Hispanics as of October 2001. This database is available online (http://www.ystr. org/usa/), free to access and was generated in order to supply the U.S. forensic DNA community with a valuable resource for frequencies of complete or incomplete 9-locus Y-STR haplotypes, as well as information about typing protocols and population genetic analyses. Pairwise R(ST)-statistics derived from the Y-STR haplotypes indicate no significant substructure among African-American populations from different regions of the U.S., nor (usually) among European-American and Hispanic populations. Thus, pooling of Y-STR haplotype data from regional populations within these three major groups is appropriate in order to obtain larger sample sizes. However, pooling of different major populations is generally not recommended due to statistically significant differences between African-American populations and all European-American/Hispanic populations, as well as between some European-American and Hispanic populations.

Online Y-chromosomal short tandem repeat haplotype reference database (YHRD) for U.S. populations.

Haplotypes from the Caucasus, Turkey and Iran for nine Y-STR loci

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Y Chromosome STR Haplotypes and the Genetic Structure of U.S. Populations of African, European, and Hispanic Ancestry

Online Y-chromosomal short tandem repeat haplotype reference database (YHRD) for U.S. populations.

Haplotypes from the Caucasus, Turkey and Iran for nine Y-STR loci