A founder effect is when a small group from one population forms a second new population. Due to the small number of founders, the genetics of the new population are different from the first one.

In population genetics, a haplogroup is a group of related haplotypes. However, in genetic genealogy, a haplogroup has come to mean a branch on either the maternal or the paternal tree of humanity.

Gene by Gene is the parent company of Family Tree DNA. It's primary owners are Bennett Greenspan and Max Blankfeld.

In genetic genealogy, a DNA segment is a length of DNA on either an autosomal DNA chromosome or the X-chromosome that is shared between two or more people.

Endogamy is the practice of marrying those from the same religious, ethnic, or other social group. It has historically been enforced by social constraint or taboo.

In genetic genealogy, chromosomes are the genetic storage units of the DNA in the nucleus of our cells. This includes the autosomal chromosomes and the sex chromosomes.

In genetic genealogy, a back mutation refers to a case where the genetic marker has had a second mutation that causes it to go back to the original value. It is most common to consider back mutations in Y-DNA STR values. However, back mutations occur in all DNA types.

Parental phasing is a form of DNA phasing done at GEDMatch with the Phasing tool. It uses one person and one or both of their parents.

While any haplogroup is also a clade, a subclade is a son or daughter branch of the clade (haplogroup) directly above it.

In human genetics and genetic genealogy, autosomal DNA refers to the twenty-two chromosome pairs that make up the human autosome.