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GENETICS & GENEALOGY

Genetic genealogy is the application of genetics to traditional genealogy. Genetic genealogy involves the use of genealogical DNA testing to  determine the level of genetic relationship between individuals.

 There are only two lasting  bequests we can  hope to give our children

 

One of these are roots

The other wings

           Hodding Carter

Welcome to Genetic Genealogy

 

To understand genetic testing you may need a minor class on the biology of a cell. There are about 3 billion, 300 million plus a few hundred thousand spots (markers/bases) that can be tested in a chromosome. A Chromosome pair has different types of markers, as new markers are found they may or may not fit into the markers already categorized.  Two known marker types used for genealogy are STRs and SNPs. A chromosome is a pair, it is not singular. One section or Chromosome of the pair is from the Father, the other to complete the pair is from the Mother. So a Pair of chromosomes. These twenty-three pairs of Chromosomes reside inside of the cell nucleus. The pairs have names, each name is a number.  Numbers One through Twenty-two, the Twenty-third pair has a different name that pair is the sex chromosome pair, it is made up of the Y Chromosome and the X Chromosome for a boy and XX for a girl. 

 

 

Study the picture below which is a boy.

The Cell of a male

 

In the 23 pairs of chromosomes 1-22 are autosomal chromosomes, these ATdna chromosomes combine and recombine. This mixing, of DNA occurs during meiosis prior to sperm and egg development. ATdna chromosomes have DNA  from both the corresponding parent’s parents (and all of their ancestors before them).. Without this you would get 100% from each parent each generation, which isn't possible, thus during recombination some of the chromosome segments sluff off, some mutate and some become silent. 

 

Next is Y-DNA, it is one part of the 23rd chromosome called the sex chromosome pair. It has no other Y chromosome to recombine with, it does develop mutations but primarily stays the same over multiple generations. 

The other part of the 23rd  or sex chromosome pair is the X chromosome. In a male child there is only one X chromosome so it basically does not recombine at this generation, but in the female child there are two X chromosomes so they will also combine and recombine during meiosis.

These are the chromosomes inside the nucleus. But there is a fourth kind of chromosome, it is not in the nucleus, but it is in the cell, it is MTdna. MTDNA is passed by the mother to her children, but only her daughter can pass it to her children. Some people get the MTDNA mixed up with the X chromosome in their heads because MTDNA is used to identify the MTDNA Haplogroup or the maternal lineage. The maternal lineage is the daughter, her mother, her mother, her mother back to the beginning of creation or when she walked out of the soup of evolution. Because there is only one set of MTDNA inherited by the children it does not combine or recombine with every generation, so it basically stays the same with few mutations over generations. Now we need to understand the actual job of MTDNA, it creates and directs energy to the cell. 

The animations at the Sorenson Molecular Genealogy Foundation website are an excellent visual resource for understanding how the 4 kinds of DNA are passed from the parents to a child. See this link:

  http://www.smgf.org/pages/animations.jspx

   

 

 

 

The sex chromosome pair is used to indicate the sex of a child. The egg always carries a X chromosome and the rest are autosomal chromosomes. The sperm  carries either the Y or the X chromosome and the rest are autosomal chromosomes.  A boy is XY and a girl is XX.

 

There are different tests used for Genetic Genealogy. There are also different markers used for the different tests. 

 

Y-DNA Tests:  The markers used for Y-DNA testing normally are called Short Tandem Repeats (STRs) this test is used to compare two men or more to find out by comparison if they are related. Then there are  single-nucleotide polymorphism (SNPs – pronounced  Snips). SNPs normally are used to identify the Y-haplogroup and for population migration. 

 

MTDNA Tests use the SNP marker.

 

AUTOSOMAL Chromosome tests use the SNP marker.

 

There are also specialty DNA tests you need to know what answers you want to figure out what test to get.

You can test the chromosomes for extra STRs and SNPs, 

 

For Information:

 SNP  - single-nucleotide polymorphism: 
 http://en.wikipedia.org/wiki/Single-nucleotide_polymorphism

  STR - short tandem repeat:

 http://en.wikipedia.org/wiki/Short_tandem_repeat

   

 

 

Y-chromosome DNA testing

 

 FROM 23and  me

 The Y chromosome is only present in males, and in one copy. Because the Y, unlike the X and autosomes, undergoes no  *recombination* (or at least very little), it travels through the generations as a block, and therefore all of its SNPs record the same  path through human history. This fact permits the ancestry of the Y to be resolved in much finer geographic detail than the  recombining chromosomes. 

 

 

 The first to understand is that to find a  Y-DNA match the haplogroup of the pair of results being compared must match.. Example a  man who has R1b haplogroup is not related  (with in the time frame of the use of surnames about 500 – 2000 yrs ago depending on the country)  to a man who has a I1b haplogroup.

 

 Haplogroups, depending on the testing company can be estimated by the first 12 STR markers of a Y-STR marker test. (normally  Y-DNA test names are  just referred to by the number of markers tested as in 12 –25-36-44-67-111) To actually prove a haplogroup  or to find a subclade of a haplogroup; a haplogroup test normally referred to as a deep clade test should be preformed. Also some companies test for particular haplogroup SNP markers. The markers tested for haplogroups are called SNPs. Go Look at this video: http://www.youtube.com/watch?feature=player_profilepage&v=A-Tjkb9gaKU 

 

After you compare the Haplogroups, you have to compare the results of the Y-SRT markers. 

look at this chart: This is an example only...

name #1 2 3 4 5 6 7 8 9 10

11 

12
 Markers DYS 393 DYS 390 DYS 19 DYS 391 DYS 385a DYS 385b DYS 426 DYS 388 DYS 439 DYS 389-1 DYS392 DYS 389-2
Man 1 12 24 14 11 11 14 12 12 12 13 13 29
Man 2 11 23 13 11 10 14 11 12 12 12 14 30

 

At number 1 they are one step of difference #2-2 steps, #3-3 steps, #4- 3 steps, #5-4 steps, #6-4 steps, #7-5 steps #8-5 steps, #9-5 steps, #10-6 steps, #11-7steps, #12-8 steps.

The total is 8 steps of difference between the two men with in 12 markers. This makes them not related with in the time frame of the use of surnames. This is only an example. But if two men are 5 or more  steps of difference between each other at 37 markers then they are not related with in the time frame of the use of surnames. the amount of the differences can increase as the number of markers tested increases. Now why is the statement  "with in the time frame of the use of surnames." important? 

 

Because it is believed that all men living today descend from one man. When he lived he wasn't the only male it is just that only his descendants  survived till today. So all men are related, just not all related within the time frame of the use of surnames. You should take the time to look up the Y- Haplogroup tree, see link below - it will help you understand. The MTDNA Haplogroup tree is different don't get them confused.

 

There are on going tests that help expand the research being done on Haplogroups, You can test for what is called Walk the Y at FTDNA or you can test for particular SNPs.

 

 

MTDNA TESTING

 

 

Parts copied from wikipedia

MTDNA is a chromosome but not part of the 23 pairs. Mitochondria are structures within cells that convert the energy from food into a form that cells can use. Although most DNA is packaged in chromosomes within the nucleus, mitochondria also have a small amount of their own DNA. This genetic material is known as mitochondrial DNA or mtDNA. In humans, mitochondrial DNA spans about 16,500 DNA building blocks (base pairs), representing a small fraction of the total DNA in cells.

Mitochondrial DNA contains 37 genes, all of which are essential for normal mitochondrial function. Thirteen of these genes provide instructions for making enzymes involved in oxidative phosphorylation. Oxidative phosphorylation is a process that uses oxygen and simple sugars to create adenosine triphosphate (ATP), the cell's main energy source. The remaining genes provide instructions for making molecules called transfer RNA (tRNA) and ribosomal RNA (rRNA), which are chemical cousins of DNA. These types of RNA help assemble protein building blocks (amino acids) into functioning proteins.

MTDNA is in both the cell of the egg and the sperm. But the mtdna of the sperm is primarily there to give energy to the sperm to swim to the egg and impregnate it. Normally all the mtdna in the sperm is used up, when it isn’t the egg cell destroys the remainder. Thus you inherit the mtdna in your cells only from your mother. That is the reason it can be used to trace the maternal lineage. MTDNA, is different from the other chromosomes in that instead of being a string it is circular, and it is normally tested in HRV1 and HRV2 and the coding zone. I was told HRV1 and 2 start basically if you were looking at a clock - at 11:59 and end at 12:06 the rest is coding zone.. and there are about 16,000 SNPs to test.

 

Your MTDNA results are different from the results of a Y-DNA numbered Test. With this test they only show you your differences from the Cambridge Standard.  To find a relationship you must match mutations. If you are going to test your MTDNA you need to understand the different tests and what they provide.  When you only test HRV1 you get a very small piece of the entire picture, That goes for testing HRV 1 and HRV2, to get entire picture that your MTDNA paints you need to test the HRV1 and HRV2 and the Coding Zones. Expensive yes...

It is hard to use MTDNA for genealogy because the maiden name changes with each generation where a man’s surname is passed to each generation. I said hard, but it is not impossible, there have been many positive results. You look for matching maiden names and area locations.. Then you put the findings together. A matched maiden name, a matched time frame, a matched location, and matching mutations.

 


Mtdna – http://en.wikipedia.org/wiki/Mitochondrial_DNA 

http://en.wikipedia.org/wiki/Human_mitochondrial_DNA_haplogroup 

 

 

 

AUTOSOMAL AND X CHROMOSOME TESTING

 


 

The chromosomes in the cell nucleus

 

 

Here is a artist interruption of a chromosome pair. 

 

All chromosomes are similar in the basics except that the smaller the numbered name the actual size is larger.

One will be the largest and 22 the smallest. You can really see this when you test your autosomal chromosomes.

 

A chromosome pair

From Wikipedia, the free encyclopedia
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.

DNA bound proteins = C (Orange here) and G (Green here)  A (red here) and T (yellow here)

 

 

 

 

Now lets discuss the newest testing.. X and Autosomal testing.  First, you inherit these 22 pairs of Autosomal chromosomes and the "X" chromosome from all your past ancestors (X chromosome   inheritance pattern is a little different then the autosomals see link - X-Chromosome chart  ), second you might think you inherit 50% from each parent. NOPE…you inherit the equal  to 50%. Since the X chromosome and the autosomal chromosomes combine and recombine randomly, (x to x; auto to auto) the further away from the common ancestor the lower the chance you have a measurable segment remaining from that ancestor. 

 

This isn't a complete example as first the solid color used for the GGF n GGM should be multiple colors as inherited from their ancestors but used for this example. 

Second each generation should show the set of pairs, not just one as this shows. Father, Mother and You show the proper pairs.

 This represents only one chromosome pair

Remember re-combination is random, there is no set pattern

 

One problem that I see with this  testing is that a negative result of a measurable segment from a common ancestor does not mean your not related, just that the part inherited is not measurable at this time.  


Autosomal Testing can have medical information, if in fact you have tested for the medical information; then make an appointment with your medical Doctor and discuss the results. Never assume just because you may have a gene that indicates you are more inclined to have an illness, that you will get that illness. Always consult with your medical doctor. Knowing that you carry a gene for an illness allows you to test often and adopt a healthier life style.  (You never know – this is cutting edge science.... five years ago.. this testing was not possible…the future holds surprises! ). 


Now here is some additional information from some very knowledgeable people..   

 

From  - Dr. Ann Turner in an email to me:  Females have two X chromosomes, one inherited from the father and the other
 from the mother, so a connection in the X chromosome could be from either side of the family.
 Males have one X chromosome, inherited from the mother. SMGF has a nice animation showing the inheritance pathway:

 http://www.smgf.org/education/animations/x_chromosome.jspx
  
 
Since not all ancestors can make a contribution to the X, you can eliminate at least some of them as possibilities. See the diagrams on Blaine
 Bettinger's site:

http://www.thegeneticgenealogist.com/2008/12/21/unlocking-the-genealogical-secrets-of-the-x-chromosome/

http://www.thegeneticgenealogist.com/2009/01/12/more-x-chromosome-charts/  
 
Note that the percentages are AVERAGES. A man's X chromosome can be exactly the same as his maternal grandfather, exactly   the same as his maternal grandmother, or a mixture of the two, which works out to be average of 50%. I find the demo Mendel family  at 23andMe helpful in visualizing this. There are three grandchildren and three grandparents, so you can look at different combinations. (for 23 & me members) If they don't show up in your list of people you're sharing with, go to Account | Sharing |   Example Profiles.    It will help you to phase the X (in other words, figure out who contributed what). This page helps tell how to do that:
http://www.isogg.org/xjourney1.html 
 
 If your genealogy program can print an ahnentafel chart, I've prepared a file with the relevant ahnentafel numbers. Females should   start the ahnentafel with themselves; males should start with their mothers. Then you can go through the ahnentafel report and  delete the records of the people who could not be the source of your X.
 http://dnacousins.com/AHN_X.TXT   

You can also google for information on genetic genealogy. There is a lot of information out there.  I am not a geneticist, this presentation is how I learned genetic genealogy, and should be used as a guide not as an absolute, please  refer to other writings about genetic genealogy for more information. You can start out by joining the different genetic genealogy lists, and or googleing for "genetic genealogy".  

 

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Nelda Percival 

administrator of four surname lists at http://www.familytreeDNA.com   Gilpin, Bonstein, Cupp, and Gillock 

Genealogy,       Y- Haplogroup,        MTDNA Haplotree,       X-Chromosome chart,       Share Your Genealogy File
About me,      About the company,      Privacy Policy
Free Forms,       For contact  - Nelda at  customerservice @geneticsand.us 

 

 

 

Answer

 

Answer to question on X-chromosome chart.:

 

The winning answer is___61____. Please explain why this is true. because it is presenting 12.5% thus stands a better chance of a segment showing up in the two cousins. 62 & 63 are only 6.25% and thus is less percentage that the segment would show up.

 

additional comments from Kathy Johnson member ISOGG

Good answer. The only clarification might be that since we have been told which ancestors the segment could have come from, the 12.5% becomes about 50% and the 6.5% now becomes about 25% each. We were essentially told to go ahead and rule out all the other ancestors in that generation in the tree. We are assuming that the paper trail has led us to particular ancestors in a specific line.

The main point I was trying to make was that people are likely to assume that the segment came from the mother (# 63) of the mitochondrial ancestor (# 31) because they mistakenly equate the mitochondrial DNA with X inheritance. Not only is that a misconception, but there is an equal chance for the segment to have come from # 62 or from either one of the parents of # 61 which would be  # 122 or # 123.
Sure, you can use this question if it makes sense.
Kathy