In humans, the Y-Chromosome spans 58 million base pairs (the building blocks of DNA and represents approximately 0.38% of the total DNA in a human cell. The human Y-Chromosome contains 78 genes, which code for only 23 distinct proteins.
The Y-Chromosome changes slowly over time and is passed along the male line, the reason why it is used to trace the paternal lineage.
How Y-Chromosome is inherited?
With each generation, if you are male, you will carry an exact copy of the Y-Chromosome that your father has had. The male descendants from two brothers who lived 500 years ago will carry the same Y-Chromosome, with the exception of eventual mutations. Mutations can happen and change the profile over time but the overall change is typically low within a family unless a very long period of time is considered. Cases of non-paternity can also affect the line and are observed to range from 10-20%.
Following the Y
Y-Chromosome studies can provide you with proof of relationship with distant cousins that share the same last name but cannot show you the female line relatives.
So, why the Y?
Because the Y does not change frequently, many distant cousins will have a very similar or even the same Y-Chromosome profile but might never meet before. This makes it an interesting and powerful tool for the genetic genealogist. It could be the catalyst for genealogists to find or confirm the information they seek.
