Wednesday, May 24, 2017

Foundational Concepts : A Summary

So there you have it.  How to understand the origins of all this DNA and genealogy stuff.  At least where the terms are derived among the branches.  Let's summarize.

1) The first and earliest DNA to be associated with family trees (doing genealogy) comes through the maternal side...known as mtDNA [name from the mitochondrial structures located out side of the nucleus].  This form of DNA gave rise to a nomenclature called "haplogroups" which were associated with geographic locations.

2)  Male descent [Y-chromosome] became the next wave of "genetic" genealogy.  As the linear sequence of the DNA contained came to be understood, all labs needed to agree upon the labeling.   Broken down by the type of changes that have occurred along this linear arrangement, another series of "haplogroups", divided even further to "haplotypes", became the rave of genealogy.  The term MRCA [most recent common ancestor ] was used to calculate a likelihood of sharing a common ancestor based upon the matches shared among folks who had this method of DNA tested.

3) The next phase of genetic genealogy expanded the population base [both male and female] that could be tested.  Using techniques that "stained" the surface of the 22 chromosomes called "autosomes", this process gave a map of the staining patterns found associated with the various types of specialized proteins called "histones".  This form of testing allowed identification of the geographic locations which clustered these changes.  Then, the various markers identified among these autosomes could be assigned to the ethic groups they represented, resulting in the "pie" figure now frequently shown.  

A simple diagram follows:

Tuesday, May 2, 2017

Foundational Concepts of DNA (3)

The various cells of the human body are assigned particular tasks.   Stomach cells produce acid, kidney cells save water, and liver cells remove certain items from the blood are all examples.  Now while each cell is carrying out its assigned function, the DNA contained in its nucleus lives in a very poorly defined form called "chromatin".   Special proteins (many provide structural and enzymatic support) are called "histones", and bind to certain areas along the DNA.  When the signal to divide and produce new cells is given, this chromatin, along with its histones, begins a cycle of  changes becoming a more visible and distinct form called "chromosomes".   Except for the ova/sperm cells, there are 22 pairs of chromosomes in each cell called autosomal.  These none sexual cells,  called "autosomes" , provide the stages for what is called "autosomal DNA".   It is the associated histones (to each chromosome) that are marked and analyzed.   This analysis becomes the bases for the reports generated.

To give a sense of the relative size of a chromosome, the follow is my attempt to draw in proportion #1 chromosome [an autosome] in relationship to the X and Y chromosomes [the sex chromosomes].

Foundational concept 3 = chromosomes package our DNA including the associated specialized helper proteins called histones.