C O N T E N T S
The Y chromosome is one of the two sex chromosomes in humans and most other mammals. (The other is the X chromosome.) It is a part of the XY sex-determination system. It contains the genes that cause testis development, thus determining maleness.
In humans, the Y chromosome spans 23 million base pairs (the building blocks of DNA) and represents approximately .38% of the total DNA in cells. The human Y chromosome contains only 78 genes, which in turn code for only 23 distinct proteins. This relationship is typical in that most species' Y chromosomes contain the fewest genes of any of the chromosomes.
Because the Y chromosome changes relatively slowly over time and is only passed along the direct male line, it may be used to trace paternal lineage. It also contains the lowest number of known genetic diseases (44 in total) related to humans.
Genes on the Y Chromosome
Y chromosome in Genetic Genealogy
In human genetic genealogy (the application of genetics to traditional genealogy) use of the information contained in the Y chromosome is of particular interest since, unlike other genes, the Y chromosome is passed exclusively from father to sons.
Paternal and maternal lineages
The two most common types of genetic genealogy tests are the Y-DNA (paternal line) and mtDNA (maternal line) genealogical DNA tests. These tests involve the comparison of the DNA of one individual to that of another to scientifically determine how many generations ago the two individuals shared their most recent common ancestor. These tests allow two individuals to determine with reasonable certainty that they are related within a certain time frame, or with reasonable certainty that they are not related within a certain time frame.
Genealogical DNA testing methods are also being used on a longer time scale to trace human migratory patterns and determine, for example, when the first humans came to North America and how they got there. One major effort currently going on is the Genographic Project, which aims to map historical human migration patterns by collecting and analyzing DNA samples from over 100,000 people across five continents.
In human genetics, Human Y-chromosome DNA haplogroups are haplogroups defined by differences in the DNA of the Y chromosome (called Y-DNA).
Y-DNA haplogroups are lettered A through R, and are further subdivided using numbers and lower case letters. Y chromosome haplogroup designations are established by the Y Chromosome Consortium .
Y-chromosomal Adam is the name given by researchers to the male who is the most recent common patrilineal (male-lineage) ancestor of all living humans.
The following is a list of sponsored public databases for Y-STR information relating to surnames and haplotypes: