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The Isaac Question and DNA Analysis

by John Plummer

The question of Isaac Sheldon's English origin has interested the author for
some years. The Bakewell, Derbyshire ancestry developed by J. Gardner
Bartlett seems probable. But it is not fully proved, and there is at least
one dissenting faction that believes Isaac Sheldon came from Devonshire or
vicinity. There were, after all, Sheldons there; and more of his neighbors
at Windsor came from there than from any other part of England. The use of
evidence from DNA has been discussed as perhaps the best possibility for
eventually proving Isaac's origin. With the recent application of DNA
analysis to the question of whether President Thomas Jefferson left
descendants by a black mistress we have come much closer to solving the
Isaac question. Indeed, we could solve it right now with luck and/or a
generous donor(s). Very shortly it should be possible to get the necessary
data cheaply and easily.

Perhaps it is best to start by reviewing the fundamentals of genetics. We
inherit discrete hereditary units from our parents, who in turn inherited
discrete hereditary units from their parents, and so on ad infinitum. These
units are called genes. Genes are made up of a molecule named
Deoxyribonucleic Acid, or DNA for short. There are four varieties of DNA
depending on which of four bases, Adenine, Thymine, Cytosine, or Guanine,
A,T,C, or G for short, are incorporated. The arrangement of these four
produces the genetic "code." The Genes in turn are part of a larger entity
called a chromosome. The cell nucleus contains paired chromosomes; while the
mitochondria in the cell outside the nucleus contain single chromosomes. The
mitochondrial chromosomes, Genes, and DNA are passed on in an unbroken
package, but only from one's mother; only in the female or matrilineal line.
It is otherwise with the genetic material in the nucleus.

Humans have 23 pairs of chromosomes in the nucleus. One of each pair is
from the father; one from the mother. Initially it would seem that no matter
how far we go back, there would be no more than 47 individual ancestors from
whom we inherit genetic material: 23 on our father's side from whom we get a
nuclear chromosome; 23 on our mother's side from whom we get a nuclear
chromosome; and one additional ancestor on our mother's side (in the direct
female line) from whom we get our mitochondrial chromosome. This would be
true except for the phenomenon known as crossing-over. Crossing over doesn't
occur with the mitochondrial chromosomes; but when the pairs of nuclear
chromosomes are splitting up they often don't follow the proper dividing
line – instead part of one chromosome will be exchanged with the
corresponding part of the other in the pair. Thus we might inherit a gene or
genes from each of our thousands of ancestors in Isaac Sheldon's generation.
This would also mean there would be almost no chance of two descendants of
Isaac Sheldon sharing any common genetic inheritance from him – except for
one last factor. One of the 23 pairs of nuclear chromosomes is composed of
unequal parts – one long, roughly "X" shaped chromosome; and one short,
often "Y"shaped chromosome. These two are known as the "sex chromosomes."
The female has 2 Xes; the male one X and one Y. A male receives his one Y
only from his father, and so the Y chromosome is carried down in the male
line. Crossing-over takes place for part of the Y chromosome; but part of
the Y chromosome is carried down intact in the male line. It is this fact
that made it possible for the Jefferson researchers to obtain meaningful
results from DNA analysis. And it is this fact which promises fruitful
results for Sheldon researchers.

The Jefferson results were revealed in the journal Nature of 5 November
1998. Briefly, descendants of Thomas Jefferson's paternal uncle, Field
Jefferson, were located; and the part of their Y chromosome which is passed
down intact was examined. There were 19 places on this part of the Y
chromosome that are found to vary among individuals. The Jefferson version
of these 19 variables was very rare – not found in a sample of 670
Europeans, or of 1,200 people around the world. A descendant of the youngest
son of Jefferson's reputed black mistress, Sally Hemings, had exactly the
same combination of variables as Jefferson's uncle. Thus this descendant was
not of African origin in the male line, but almost certainly a Jefferson
descendant in the male line.

Members of the Sheldon Family Association descend from several Sheldon
immigrants. The three main branches come from Isaac Sheldon of Windsor,
Connecticut 1652; Godfrey Sheldon of Scarborough, Maine by 1660; and John
Sheldon of Newport, Rhode Island 1652. Godfrey Sheldon definitely came from
Bakewell, Derbyshire, England. The other two have been thought to have come
from Bakewell as well, but proof is lacking. If male line descendants of
Godfrey Sheldon have the relevant part of their Y chromosome tested; if it
is a relatively rare type; and if the male line descendants of Isaac and
John have the same type; then it may be presumed that all three came from
the same Bakewell family. Otherwise, they would not be from the same family,
and it would be very likely that they came from another part of England.
Theoretically two or more Sheldon families with different paternal
ancestries could have originated from the small hamlet of Sheldon in the
parish of Bakewell; practically, however, the author doubts that this is a
common occurrence. The location and testing of English Sheldons, including
ones from other parts of England than Bakewell, would be desirable, but not
immediately necessary.

The final solution of the Isaac question may be broken down into four
steps. One – locating male line descendants of the different Sheldon
immigrants. Two – obtaining DNA samples from as many of the above as
possible. Three – analyzing the DNA from the above, preferably for all 19
variables. Four – interpreting the results of the analysis. The Sheldon
Family Association has already done the first. The last is no problem
whatsoever to carry out. A new facility now makes step two readily doable.
Only step three would be at all difficult to have done right now; but it may
soon be easily carried out as well. In 1996 Edwin M. Knights, M.D. and
George A. Fischer, Ph.D. of Life Science, Inc. established that
organization's Gene Saver Division, which has been featured in a number of
reputable genealogical periodicals. Kits to take a drop of one's own
fingertip blood are available by mail from Gene Saver (Box 1303, Grantham, NH
03753) for $5 for one to three samples, going down to $1 per sample for nine
or more. The samples then should be returned to Gene Saver to be processed by
lyophilization and preserved in specially sealed and marked containers. This
step costs $57.50 per sample for the processing, $20 to $35 for a custom
engraved preservation container, and $9.95 for postage for any number of
containers. The samples are returned to the individual or organization. They
are then ready for DNA analysis when that becomes available. Dr. Knights
writes that he expects "a more competitive analytical climate in the near
future" resulting in "a laboratoriy that is both inexpensive and reliable."

It would be advantageous for the Sheldon Family Association to obtain as
many samples from male line Sheldons as possible. Multiple samples for each
immigrant are desirable to guard against possibilities of illegitimacy and
sample contamination, deterioration, or mixup. Also, further useful
information might be available because of possible small mutations in the
last three and a half centuries. Once the first samples are obtained it
might then be decided to seek immediate analysis, though that would be
expensive and hard to secure. Or we might patiently wait until a laboratory
tailored to our needs develops, probably in the near future.

About the Author: John Plummer has a B.A. from New
England College majoring in History and specializing in English History of
the Tudor and Elizabethan periods. He is working on his M.A. in Early Modern
European History at Columbia University specializing in the history of the
English Puritans. He started genealogy research when he was 10 years old. He
has worked as a free lance genealogist since graduating college in 1973. He
belongs to so many historic and genealogical societies that he has lost
count. He has published works on history and genealogy in The
Connecticut Nutmegger
, National Genealogical Society Quarterly, The American Genealogist, The New England Historical and
Genealogical Register
, Descendants of the Founders of Ancient
Windsor Newsletter
, and numerous family association newsletters.

(email the author)