• Introduction to Molecular Genealogy
• Family Tree
• DNA Testing
• Your DNA
• Mitochondrial DNA
• Y Chromosome DNA
• Autosomal DNA
• X Chromosome DNA
• Haplogroups
• Mutation and Haplotypes
• Putting it all together
• How to use a DNA kit
• Understanding your results

X Chromosome DNA

The X chromosome is one of the chromosomes that determines gender. Females have two X
chromosomes. Males have one X and one Y chromosome. In a Mother, the X chromosomes behave just like autosomes. Her X chromosomes go through recombination, then she passes one along to each child, regardless of whether the child is male or female.

A father passes a copy of his X chromosome to his daughters, but not to his sons. Since he has only
one X chromosome, it does not go through recombination. Because of its unique inheritance pattern, X chromosome DNA contains genetic information from some but not all of a person’s ancestors.
X chromosome DNA becomes more fragmented through the generations, although not as quickly as
autosomal DNA. Like autosomal DNA, it is more informative about our more recent ancestry.