Ydna Testing Paternal Genetics

Y-DNA, which is only passed from father to son, is an important tool in human genetic genealogy, and is used to determine information about paternal ancestry. Molecular genetics can tell a male if a potential ancestor is closely related by comparing Y-DNA markers.

Similarity between Y-DNA sequences suggests that two individuals share a more recent ancestor. This can be very helpful in increasing the accuracy of a pedigree on surnames or determining ethnicity, such as using Hebrew Y-DNA to determine if one is a descendant of the Cohanim, a prominent historic family of Jewish priests.

Biology of Y-DNA

Most mammalian cells have two sets of chromosomes. Males have a Y-chromosome and an X-chromosome. Females have two X-chromosomes.

Y-DNA refers to the DNA in the Y-chromosome of the male. This DNA contains the SRY gene, which drives development of the organism into a male. The Y-chromosome is comprised of 58 million base pairs (bp) which make up 86 genes. These genes code 23 proteins. As might be expected, since only half the population has the Y-chromosome, Y-DNA contains no vital genes necessary for life.

Holandric traits are those that are inherited through the Y-chromosome. Most of the Y-chromosome does not recombine with the X-chromosome and is termed the non-recombining region of the Y-chromosome (NRY). A small part of the Y-chromosome, which is not involved in determining traits, is passed from father to son. Single nucleotide changes or polymorphisms (SNP’s) in marker regions are used to trace direct paternal ancestral lines.

Y-DNA and Genealogy

Many types of ancestral DNA tests exist which attempt to determine an individual’s genealogy. Mitochondrial DNA is used to trace maternal lineages since DNA in the mitochondria is only inherited from one’s mother. Y-DNA is used for the male lineages since sons inherit their Y-chromosome DNA entirely from their father. By comparing genetic evolutionary trees and family history research, one has a better chance of determining who one’s ancestors are.

Random and subtle genetic mutations occur as DNA is passed on from father to son. These mutations occur about every 500 generations. When they occur, they are inherited in future generations. By counting the number of mutations between two individuals, one can determine how closely related an ancestor is. These mutations allow researchers to identify individuals into haplotypes.

An evolutionary tree can be established showing where these mutations occurred. Many individuals can be assembled into haplogroups by following the branches on the tree. Others must undergo further testing for SNPs. This allows one to also determine paternity, pedigrees and the ethnicity of the paternal lineage.

In 1997 the Cohanim Project tested Jewish Y-DNA from men of different origins who claimed to be descendants of Cohanim, or Temple priests. This project confirmed that many of the men were indeed descendants. This is important because the Cohanim are purportedly the direct male descendants of Moses’ brother Aaron.

The company Family Tree DNA now holds hundreds of thousands of samples in their comparative database for people to use to help determine their ancestry. This type of database can build new connections. But some people have discovered that their origins are not what their families have thought for generations.

Controversy and Popularity of Y-DNA Paternity Testing

There are many questions surrounding paternity testing. Some think it is not conclusive, trustworthy or safe. Paternity tests are, however, worth believing. An individual cannot falsify test results because DNA is obtained directly from the father and mother.

The protocol is simple and followed carefully. Fingerprints are taken for safeguard, so one cannot give another person’s DNA. A collection of cells is taken from the inside of the cheek with a cotton swab. Tests are duplicated by separate laboratories. The results are 99 percent reliable. Drinking alcohol, taking breath mints or brushing one’s mouth will not change your DNA result.


Dardashti, S.T. (2008). When oral history meets genetics. Retrieved September 11, 2008, from the Jerusalem Post Web site: www.jpost.com/servlet/Satellite?cid=1206632365879&pagename=JPost/JPArticle/Printer

DNA Paternity Tests. (n.d.). DNA test or why cheating DNA test is a bad idea. Retrieved September 11, 2008, from the DNA Paternity Tests Web site: www.dna-paternitytests.com/dna-testing/Fake-DNA-Test.html

Montgomery, D. (n.d.). Genetic genealogy: The new frontier. Retrieved September 11, 2008, from the Worldwide Ancestry Research Services Web site: www.wars-genealogy.co.uk/genetic_genealogy.htm

World Families Network. (2008). Y-DNA testing. Retrieved September 11, 2008, from the WorldFamilies.net Web site: www.worldfamilies.net/ydna