1. The Complicated and Unruly X Chromosome

2. Actual Images of the Two Sex Chromosomes The Bix X and the Little y
These are actual Scanning Electron Micrographs of the X and Y chromosomes that we conveniently stained blue and pink to reflect the female male connection.
Scientist believe the Y Chromosome is getting smaller over time. What do you think that means?

3. X Inheritance Pattern
Whenever two of the same type of DNA get together during egg or sperm manufacture they tend to intermingle and exchange bits of their DNA with each other. This is a process known as Meiosis. Thus the X that the Female gets from her mother is more than likely a blend of the 2 X chromosomes the “mum” had. And, of course, her 2 X’s came from her mom and dad. Thus we get that “uniqueness” that makes us all different. This is especially true of the other 22 chromosomes known as the “autosomes”. HOWEVER, note the X that came from dad. It was there with a Y chromosome so no mixing is possible. So dad passes on to his daughter the same X he got from his mother unchanged.
Also note the Y chromo. being passed Father to Son. It also has nothing to mix with. Thus ALL Y chromosomes are passed from father to son, over possibly hundreds of generations with no change unless there is a mutation. If that mutation is significant, a new “haplogroup” may be formed. More of that in a separate class.

4. Note there is no X history transferred from the left side
Note there is no X history transferred from the left side. That is because the Dad only passed on his Y Chr. to his son.
If Dad’s GF and GM did not have a daughter, all the info for the the X chromosome is lost forever. At least for this genetic strain
But, while passing on an unchanged Y creates a long line of males, the opposite is true for the X. If a couple has only males, the X chromosome history of the dads side is lost. Only the X history from the Mom’s side is passed along.

5. On the other hand, if Mom and Dad have a daughter, Dad’s X DNA is passed on and the history the X is continued, but only for GM’s branch.
So if a female gets 2 X’s, do they get mixed during the transfer like autosomal (1-22) chromosomes?
But even when the couple has a daughter, 25% of the X history is lost from the dad’s father’s line. Thus the X chromosome can NEVER be a mechanism for generational research.

6. This is the way ‘recombination’ is supposed to work
We could spend the entire class trying to understand this table.
Key points to remember:
1)Because an X-chromosome is passed exactly from father to daughter, it will remain unchanged for that generation. This means that X chromosomes change less often along father-daughter pedigree lines.
2) The Mom transfers one of her two X chromosome which may or may not have been mixed with her other X chromosome
This is the way ‘recombination’ is supposed to work
Unless you want a headache, don’t bother to try understanding this table. Just think about the two notes. The ‘may or may not have been mixed . . ‘ is a key phrase

7. The two X Chromosomes of a female may re-combine when a new egg is made, but not the X the father passes on since he has only a single X paired with a Y. There is nothing to re-combine with
Mixing or “re-combining” of the X is an important factor. So we are going to look at it in detail. This is what the DNA Geneticists thought would happen from generation to generation. However, when they started analyzing how much recombination took place during Meiosis, there were a bit surprised. The average recombination events for the 22 Autosomes is events per long arm. In contrast the X only has 8 to 24 events for the whole chromosome with some percentage that has no exchange at all. What does that mean and how does that effect who we are? Big questions with no real answers.

8. Plus XX (girl) or XY (boy)
This is where it all starts.
Egg=
22 autosome chromosomes
Plus an X
Sperm=
22 autosome chromosomes
Plus either an X or a Y
This slide is self explanatory. The egg has its 22 autosomes and an X from mom (which may or may not have been re-combined) which is half of the normal allotment of 46 Chromosomes (23 from mom – 23 from dad). The sperm has 22 autosomes from dad and either another X from the dad’s mom meaning the baby would be a female or a Y from his dad.
Note that males are a prodigious producer of sperm. New sperm are created at a rate of 1,500 per second!! That’s right – per second. The typical quantity of sperm per ejaculation is 15 Million. And, after that one lucky sperm penetrates the egg cell wall and immediate change occurs that blocks any other sperm from getting in.
Baby=
44 autosomes
Plus XX (girl) or XY (boy)

9. DNA Analyzed for Youngest Son’s Family
Maternal Side
Paternal Side
Grandfather – L.T
Grandmother- S.L
Mom – A.T.
Dad– T.L
Son – R.T.
Prev. Marriage
Daughter
P.F
Due to the great Christmas FTDNA sale, I have the good fortune to have three generations to analyze.
To reduce clutter and increase clarity not all DNA results included

10. So how did my Grand Daughter’s (P.L.) DNA get mixed?
FTDNA Chromosome Browser (colored bar indicates a DNA match in each Chromosome)
Gold - Half Brother – R.L. (total match = 24%)
Green – Maternal Grandfather – L.T. (total match =21%)
Blue – Paternal Grandmother – S.L. (total match = 24%)
(Note the Blue 100% match on the X Chromosome)
These graphs are generated by the FTDNA’s Chromosome Browser tool. Up to four other individuals can be compared to the base individual. In this case the base person is my Grand Daughter P. L. The left side shows all 22 autosomes and the X sex chromosome. The gold is the DNA of her half brother (same mother – different father) Green is her maternal Grand Father. And Blue is her Paternal Grandmother, my wife. Where ever there is a colored bar, it means that our Grand Daughter has a DNA match in that area of the chromosome. As might be expected from the recombination of the chromosomes, the total match is in the 21 to 24% range. There are some interesting patterns. Note the almost total match with her grand father for Chr. 12 and 13. But even more interesting is the almost total match with her paternal grand mother for Chrs. 3,4,6,and 8 and the complete 100% match for the X Chr. See the next slide for further discussion of the X Chr.

11. X Chromosome Inheritance
The Blue at the bottom of the image indicates where a “match” occurs between GD and GM. In this case it is a 100% match. But note the top is primarily Yellow. That indicates a “half match”. That is because GD gets two X’s. The other would always be a 100% with her mother.
So this is common
Grandmother (GM) to Granddaughter (GD)
See the explanation in the slide.

12. Chromosome Browser for adopted Grandson
Gold- Half Sister (total match = 24%)
Blue – Mother (total match = 100%)
Green – Maternal Gradmother (tot. match = 32%)
(Note the Green Bar in the X Chromosome)
Now, when we add in the maternal Grand Father’s DNA. Note there is another 100% match for the X chromosome. This not expected since normally the X contributed by the GF to his Daughter would have been mixed with the X contributed by the GM to her daughter. It should have been more like 50% to 75% max. And it gets even more interesting when compare the Mother’s contribution of X DNA versus the GF contribtion. See the next slide

13. X Chromosome Inheritance
Mother to Son
As should be expected, there is a 100% match on the X chromosome from Mother to Son since he received the X only from her and a Y from dad. Note, however, that it is a half match (yellow) since he only received one of her two X chromosomes
Let’s explain that half match further. Note that the equipment used to analyze the X DNA can NOT separate the 2 X Chr’s in the mother’s DNA. Both are read at the same time. So it is by definition a composite of the X DNA the mother received from her mother and the X DNA received from her father. And even though the son only received one X Chr., there is no way to determine which X the daughter received. Thus it will always be a “half match” when comparing to his mother. However, we can also compare the X DNA the son received from his GF. See the next slide.

14. X Chromosome Inheritance
This “match” is much more unusual. As noted in Slide 7 , the X Chromosome tends to recombine from generation to generation. But not always. Note the graph is both all Blue, but also all Green. Which indicates a 100% Full match between the Grandfather and Grandson. That means the Grandson has the exact X DNA that his Great Grandmother was born with almost two centuries earlier.
Grandfather to Grandson
The notes on the slide sum it up well. So how unusual is this? Not that much work has been done to analyze how often this phenomenon of X DNA being transferred with no recombination. The best estimates I could find were in the 3-4% range. However, in the only other 3 generation study I could find, 1 of the 3 GS’s had a non-recombined X from his GF. So what is the actual percentage? No one knows. And even, more importantly, what does it mean? What are the advantages (if any) of transferring the X Chr. Un-recombined over 3 or more generations? Stay tuned.
Now let’s look at just what the X DNA contributes to your overall functioning.

15. So what does all this mean. How is X DNA used in the body
So what does all this mean? How is X DNA used in the body. As the presentation title suggests:
!*!*! It’s complicated !*!*!
Related Diseases: 1 in every 650 births has an X Chromosome related disease
Klinefelter Syndrome – Male inherits both X’s from mother,
thus XXY instead of XY. Symptoms: lack of body hair,
enlarged breasts, Narrow sloped shoulders.
TARP Syndrome – Club foot, Heart Arterial Deformities
DENT Disease – Chronic Kidney Disorder
Slide is self explanatory.

16. Microphthalmia – Small Eye Syndrome
Forest Whitaker Jennifer Hudson Penelope Cruz
So the X chromosome is not just related to whether a fertilized egg becomes Male (XY) or Female (XX). It has over 1,000 genes. Beside the various X related diseases listed above, and that is a small sample, an area that is getting much more attention is the “in- or de-activation” of one X chromosome in every new cell made from the fertilized egg. That seems to make sense. Why would you need two X chromosomes since the genes are the same in each X. You only need one, right? Not exactly, it’s complicated. .
Slide is self explanatory

17. Which one is In- De-activated – the male donated X or the female X
Which one is In- De-activated – the male donated X or the female X? Early on geneticist thought it was random. But new studies show that is not always the case. Note the pictures below. Scientists developed a way to stain the X chromosome from a female mouse Green and the male X chromosome Red. These are images of a mouse’s retinas. Why is the left retina primarily male X and the right mostly female X?
A calico cat (always female) is another example. The orange and black are the result of different X de-activation. White means no pigment
Slide is self explanatory

18. History of miscarriage, Deficit of live male births, or
Cases have been found where there is a 95:5 ratio of forced male or female X chromosome deactivation. In those cases there is invariably a disease process included. Those disorders include:
History of miscarriage,
Deficit of live male births, or
An otherwise unknown cause of mental retardation in a male family
member.
Non-deactivation is also present in cancer cells. Several forms of breast cancer have cells where both X Chromosomes are active.
Slide is self explanatory

19. !*!*! It’s Complicated !*!*! Summary XY – Male XX – Female
An X chromosome may go several generations without recombining, especially in the father-to-daughter transfer. Estimates are that occurs in 3-4% of new babies, but that may be low.
X Chromosome contains over 1,000 genes affecting much more than sexual orientation. 1 in 650 births have some form of X related disease.
Very early in new cell development one of the two X chromsomes in a female cell is “in- or de-activated” supposedly random between male and female contributed X’s BUT evidence is accumulating that is not always the case and the consequences may be good or bad.
!*!*! It’s Complicated !*!*!

20. Dave Lewis – “Semi-Pro DNA Genealogist”
(916)
Available for Consultation and/or Tutoring