Y chromosome testing falls under relationship DNA testing. Relationship tests are used to establish various types of biological relationships between alleged relatives. The Y chromosome test is used specifically between males as it is only males who carry this chromosome.
Humans have two sex chromosomes; females have XX chromosome pairs and males have XY chromosome pairs. Each of us has 23 of these pairs though it is possible for some people to have chromosomal disorders in which people have more than 46 chromosomes.
Only males have the Y chromosome and it is this chromosome that is involved in the development and characteristics of the male sex. Some genes are unique to each of the X or Y chromosome but there are certain genes which are found on both, such as, for example, the amelogenin sex gene. These regions which are found on both chromosomes are called pseudoautosomal regions. The total number of genes we have in our body is somewhere between 20,000 and 25,000.
When is the Y chromosome test used?
The Y chromosome test is used in cases in which two males want to know whether they share the same father. In this case, a Y-chromosome test will trace their profiles and if the two profiles match, then the test can conclude that they are at least half brothers and share the same father.
When doing a Y-chromosome test instead of a paternity DNA test there is one main issue to consider: if the two males being tested think they may be related from the father’s side but not be actually brothers (perhaps first cousins) the test becomes redundant. Y chromosome testing will tell you that you share the same paternal line but not that you share the same father unless males being tested can exclude other possibilities of relationship between themselves other than siblings.
The test can also be used in genealogy and ancestry testing; the Y chromosome remains relatively unchanged from one generation to the next and thus, the Y chromosome test is a good way of tracing male lineage and establishing the existence of relationships even between relatively distant relatives.
Sampling for DNA tests nowadays can simply be done using an oral mouth swab. The DNA sampling for a Y chromosome test can also be done in this simple way.