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Base Pair

The base-pairs are what form the rungs on the double helix “ladder” known as DNA. There are only four basic molecules (nucleobases) that, when in their paired form, form the “rung” of the ladder. These four molecules, known more commonly just by their first letter, are A, T, C and G. As A only ever matches with T and C only ever with G, you can split the rungs (helix) into each side and read either set of values. Nomenclature is used to define which side and from which end you are specifying the sequence of values in a particular DNA strand.

SNP markers are defined for a specific rung on the ladder (location, or locus) where the base-pair value is observed to change. Often, swapped from left to right. Sometimes inserted or deleted. And even fewer times, a sequence of a few base pairs may change. STRs are definitions of non-coding region DNA (that is, not in genes), where there simply appears to be a replication in the sequence of base-pairs. Either of a particular rung value (nucleobase) or of a short sequence of rung values.

In genetic genealogy, we tend NOT to measure the length of a segment of DNA as the number of base-pairs but more using a form termed centiMorgans.

Nucleobases, when constructed with more of the molecules to build the “side rail” that will hold them together in a sequence, are termed Nucleotides.

In genetic genealogy, these distinctions between the base-pair, the individual nucleobases or even the nucleotides are not important and you may see the terms used somewhat interchangeably by the genealogist.

For the purposes of genetic genealogy and its resultant testing, you do not need to really know the names of the various forms of nucleobase molecules and forms; or of the amino acids they form when in specific larger groupings. Just remember the fact the four exist and are the basis of reporting results in the RAW data files.

We purposely have kept this section simple, short and lacking of the detail. It only serves to confuse the genetic genealogist not familiar with the chemistry and is not necessary to know when utilizing genetic genealogy testing. Please refer to further references here and found on your own to delve more into the details and terminology.

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