Y-DNA vs. mtDNA vs. Autosomal

A complete guide to the three main types of consumer DNA tests and what they can (and cannot) tell you about your ancestors.

When most people say they "took a DNA test," they are referring to Autosomal testing. However, genetic genealogy relies heavily on three distinct biological pathways of inheritance.

1. Autosomal DNA (atDNA)

This is the standard test offered by AncestryDNA and 23andMe. It tests the 22 pairs of non-sex chromosomes. You inherit exactly 50% from each parent. Because of recombination, autosomal DNA is highly effective for finding recent cousins (up to 3rd or 4th cousins) but becomes statistical noise beyond 6 or 7 generations.

2. Y-Chromosome DNA (Y-DNA)

Y-DNA is passed strictly from father to son. It rarely recombines or mutates. This makes it a powerful tool for tracing the direct paternal line (surname line in many cultures) back tens of thousands of years. Only biological males can take a Y-DNA test.

3. Mitochondrial DNA (mtDNA)

Mitochondrial DNA is found in the mitochondria of the cell, outside the nucleus. It is passed strictly from mother to child (both male and female). Like Y-DNA, it mutates very slowly, allowing you to trace your direct maternal line back to "Mitochondrial Eve."

Common Mistakes

Testing your Y-DNA will not tell you about your mother's father. Testing your mtDNA will not tell you about your father's mother. They represent only two specific branches of your massive family tree.

Frequently Asked Questions

Which test should I take to find my grandfather? Autosomal DNA is the only test highly reliable for recent 20th-century genealogical brick walls.

Next Step: Understand the limits of ethnicity in our Ethnicity Estimates guide.