genealogy: the science of the word

Genes are the basic units of heredity. A gene is a short piece of DNA, which tells the body how to build a specific protein. There are approximately 30,000 genes. The combination of all genes makes up the blueprint, or plan, for the human body and its functions. A person's genetic makeup is called a genotype.

logy taken from the Greek word logos is a prefix meaning the study of oral or written expression as in phraseology; or doctrine, theory, or science as in ethnology.

When these two parts are combined, it is clear that genealogy is the study of a person's ancetory:

ge·ne·al·o·gy
1 : an account of the descent of a person, family, or group from an ancestor or from older forms
2 : regular descent of a person, family, or group of organisms from a progenitor or older form : PEDIGREE
3 : the study of family pedigrees
4 : an account of the origin and historical development of something