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. 

Monday, April 3, 2017

Foundational Concepts of DNA (2)

Corporate headquarters for your DNA is the nucleus.  At the same time, multiple branch offices reside scattered around that part of the cell out side of the nucleus called the "cytoplasm".  These branch offices are called "mitochondria" and contain a much smaller, circular shaped DNA passed down from the moms of the world.  You have come to call this mtDNA [ for this unique form of circular DNA located in the branch offices].   A big picture of this single cell organization is shown.

The yellow area is the nucleus.  The clear moist looking area is the cytoplasm.  Within each branch office [mitochondria] are specialized copy machines called "ribosomes".  Communication between the home office and all the branches use special messengers to carryout the purpose of this organization called RNA [ribonucleic acid].  Three RNA forms exist called messenger RNA... transfer RNA... and ribosomal RNA.  Universally accepted as the central tenant, the purpose of DNA is to make proteins:  1) new DNA is copied from the existing DNA, 2) messenger RNA is copied from DNA, and 3) proteins are made from this messenger RNA.  Wow...what a deal.

Monday, March 13, 2017

Foundational Concepts of DNA

The DNA revolution has produced a number of new opportunities for the eager genealogist.  Along with these opportunities come a host of unusual terms, fancy words, and confusing outcomes that can make for some, a very difficult experience.  For those, who like me, continually express...say what!...this post will begin perhaps a series of posts on some basic ideas surrounding all this DNA stuff.   So, let's begin.

Our human existence is dependent on the cell, the basic unit of life.  All  "us humans" are made up of these cells, and come from cells.  As we know it, one of the most important aspect of these cells is reproduction.  [Good thing or we would'nt be here!]  At any rate, it is during this reproduction that our genetic traits get pass down.  Now this DNA ( doxyribonucleic acid ) is the molecule of inheritance for all.  These poor cell's DNA is the thing that gets knocked around in all these labs...scraped, dipped, broken apart, multiplied, electrified, analyzed, and...the results printed out, as the "Holy Grail" of our long lost relatives still among the family tree.

The basis for most traits past down is the functional unit of inheritance call the "gene".  Each gene is given a specific position (location or loci) along the DNA molecule to be preserved and transmitted on down the family tree.  These genes control our biological processes through the production of proteins and a special modification called RNA ( ribonucleic acid ).  The genetic composition of all genes is called the "genotype".  The observable inherited traits [ physical, behavioral, physiological, etc.] is given the word "phenotype".

Foundational concepts 1) Genes form the basis of our inheritance.