ST A measure of the subdivision between populations that takes into account the molecular distance between haplogroups/haplotypes, as well as their frequency.
ST A measure of the subdivision between populations that takes into account the molecular distance between haplogroups/haplotypes, as well as their frequency.
AZOOSPERMIA The absence of sperm in the ejaculate.
BALANCING SELECTION Selection that favours more than one allele, for example, through heterozygote advantage, and so maintains polymorphism.
EFFECTIVE POPULATION SIZE The size of an idealized population that shows the same amount of genetic drift as the population studied. This is approximately 10,000 individuals for humans, in contrast to the census population size of >6 
109.
ENDOGAMY The practice of marrying within a social group.
EUCHROMATIN The part of the genome that is decondensed during interphase, which is transcriptionally active.
FREQUENCY-DEPENDENT SELECTION Selection that favours the lower-frequency alleles and so maintains polymorphism.
GENE CONVERSION The non-reciprocal exchange of sequence.
HAPLOGROUP A haplotype that is defined by binary markers, which is more stable but less detailed than one defined by microsatellites.
HAPLOTYPE BLOCK The apparent haplotypic structure of the recombining portions of the genome, in which sets of consecutive co-inherited alleles are separated by short boundaries; there is debate about the origins of haplotype blocks and whether the boundaries correspond to recombination hotspots.
HOLOCENE The 'wholly recent' geological period that spans the past 
11,000 years and is characterized by an unusually warm and stable climate.
HOMOLOGUES Genes or sequences that share a common ancestor.
HOMOPLASY The generation of the same sequence state at a locus by independent routes (convergent evolution).
LINKAGE DISEQUILIBRIUM The non-random association between alleles in a population owing to their tendency to be co-inherited.
MICROSATELLITE A class of repetitive DNA sequences that are made up of tandemly organized repeats that are 2-8 nucleotides in length. They can be highly polymorphic and are frequently used as molecular markers in population genetics studies.
MULTIFURCATION/BIFURCATION The splitting of an ancestral lineage into two or more daughter lineages.
NRY, NRPY AND MSY Several neologisms have been introduced to refer to the portion of the Y chromosome that excludes the pseudoautosomal regions, for example, non-recombining Y (NRY), non-recombining portion Y (NRPY) and male-specific Y (MSY), but none has achieved wide acceptance.
PARAGROUP A group of haplotypes that contain some, but not all, of the descendants of an ancestral lineage.
PARALOGUES Sequences, or genes, that have originated from a common ancestral sequence, or gene, by a duplication event.
PHYLOGENETIC TREE A diagram that represents the evolutionary relationships between a set of taxa (lineages).
PHYLOGEOGRAPHY The analysis of the geographical distributions of the different branches of a phylogeny.
RECOMBINATION The formation of a new combination of alleles through meiotic crossing over. Some authors include intrachromosomal gene conversion under this heading. As this has been shown on the Y chromosome, they prefer not to refer to it as 'non-recombining'.
SATELLITE DNA A large tandemly-repeated DNA array that spans hundreds of kilobases to megabases.
XX MALE An individual with a 46,XX karyotype but a male phenotype rather than the expected female phenotype
