The Y Chromosome Markers Examined

DNA samples from each of the 19 blood specimens gathered by Dr. Foster were carefully extracted by a pathologist at the University of Virginia (Murray and Duffy 1998). The DNA samples were coded by Dr. Foster and then taken to England where researchers at Oxford University examined them. Eventually the team of scientists involved expanded to include researchers from the University of Leicester in England and Leiden University in the Netherlands. A variety of tests were run independently at these three locations (Foster et al. 1998).

The Y chromosome markers used in this study are listed in Table 9.8. In all, there were 19 Y chromosome markers examined in this study. These included 11 STRs, seven SNPs, and one minisatellite MSY1, which proved to be the most polymorphic marker.

DNA Marker

Field

Eston

John Carr

Thomas

Tested

Jefferson

Hemings

Male-Line

Woodson

Male-Line

Male-Line

Male-Line

Number of

5

1

3

5

individuals typed

Y STR Loci

DYS19

15

15

14

14

DYS388

12

12

12

12

DYS389A

4

4

5

5

<

DYS389B

11

11

12

11

DYS389C

3

3

3

3

DYS389D

9

9

1O

1O

DYS390

11

11

11

11

DYS391

10

1O

1O

13

DYS392

15

15

13

13

DYS393

13

13

13

13

DXYS156Y

7

7

7

7

Y SNP Loci

(0 = ancestral state; 1 = derived state)

DYS287 (YAP)

O

O

O

O

SRYm8299

O

O

O

O

DYS271 (SY81)

O

O

O

O

LLY22g

O

O

O

O

Tat

O

O

O

O

92R7

O

O

1

1

SRYm1532

1

1

1

1

Minisatellite Locus

MSY1

(3)-5

(3)-5

(1)-14

(1)-14

(1)-

-17

(1)-

-16

(3)-32

(3)-32

(3)-36

(3)-27

(4)-16

(4)—16

(4)-21

Y chromosome markers and results used to trace Thomas Jefferson's maleline ancestry (Foster et al. 1998). The Field Jefferson (uncle of President Thomas Jefferson) maleline matches the Eston Hemings (youngest son of Sally Hemings, one of President Jefferson's slaves) male-line exactly. The numbers shown in the table represent the number of repeats observed for each Y chromosome marker Arrows have been placed next to the alleles in the Y haplotypes for John Carr and Thomas Woodson male-lines that differ from the Jefferson males.

All 19 regions of the Y chromosome examined in this study matched between the Jefferson and Hemings descendants. These DNA results were viewed by Dr. Foster and his co-authors as evidence for President Thomas Jefferson fathering the last child of Sally Hemings (Foster et al. 1998). Interestingly the John Carr and Thomas Woodson's male lines differed significantly from the Jefferson-Hemings results (Table 9.8). At least seven of the 19 tested DNA markers gave different results. Thus, Thomas Jefferson could not be linked as the father of Thomas Woodson nor was Samuel Carr or Peter Carr the father of Eston Hemings. The results of the Virginia old-line families were not reported, presumably because these samples served their purpose as effective controls and revealed no unusual Y chromosome patterns.

In this study, Y chromosome markers demonstrated their usefulness in monitoring paternal transmission of genetic information by tracing the male lineage of Thomas Jefferson across 15 generations (Figure 9.10). The ability to connect Y chromosome DNA information across the generation gaps meant that living relatives could be used in this investigation rather than disturbing the almost 200-year-old burial site of President Jefferson.

Figure 9.10 Ancestry of Thomas Jefferson and Eston Hemings male lines. The shaded boxes represent the samples tested by Foster et al. (1998) in their Jefferson Y chromosome study. A male descendant of Eston Hemings, son of Thomas Jefferson's slave Sally Hemings, was found to have a Y chromosome haplotype that matched male descendants of Field Jefferson, President Thomas Jefferson's uncle. A male descendant of Thomas Woodson, claimed by some to be descended from Jefferson, had a different Y haplotype and therefore could not have been a Jefferson.

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