Download Presentation FZ4201

Presentation FZ4201
Slide 1
Slide 2
The sample of the study consisted of 400 males which were typed for their minimal
haplotype. 200 of these were typed for an additional 7 Y-STR’s. 2 -13 alleles
maximum were observed and 146 different haplotypes were observed using only the
minimal haplotype. The geographical distribution for 22 individuals of known
paternal origin was also determined.
Slide 3
From these 146 haplotypes, 90 or 22.5% from the whole sample were identical.
Especially when you look at 3 subpopulations in the South of Finland namely Savo
with 53%, Pokjanmaan with 42% and Karlaja with 37%.
With the 7 additional loci, 120 haplotypes were identified and individuals sharing the
most common haplotype decreased to 13%.
Slide 4
In comparison with other populations from Europe, the Finnish population showed a
significant decrease in genetic diversity when the number of different minimal
haplotypes was divided by the sample size. 36.5% for the Finnish population
compared to 83.7% on average in a European population. These numbers strongly
support the earlier hypothesis on which this study was based, of individual isolated Ychromosomal lineages and population substructuring in Finland.
Slide 5
Power of exclusion was tested for the Finnish population. 200 real cases were
examined. Of these 200 cases, 100 provided an inclusion and 100 an exclusion. Of
these 100, 92 had one or more allele difference, 8 showed no difference and 20% had
2 or less differing Y-STR alleles.
Slide 6
What has caused this decrease in genetic diversity compared to other European
populations? Finland has a special population history: because of its geographical
boundaries, it is relatively isolated and population numbers have been, and still are,
very low, with very little migration. Now it has an estimated population of 5.100.000.
About 4000 years ago a small number of founders, separated and isolated themselves
from the larger population and settled more in the South of Finland where more
cultivative land was available and where they could avoid the increasing taxation of
the Swedish Crown.
Slide 7
This internal migration caused a Founder Effect where genes occurring at a certain
frequency in the larger population will occur at a different frequency in a small subset
of that population. This phenomenon taken together with random inbreeding
increased the frequency of some rare diseases and in some, a regional clustering can
be observed, reflecting the regional origins of the founders. Other disease alleles
became almost non-existent. And this is what they call the Finnish disease heritage
and why researchers are so interested in this population.
Another probable cause of this drop in genetic diversity and increase in specific
genetic diseases is suggested by the authors to be a bottleneck. They base their theory
upon the figures we showed you earlier of 36.5% and 83.7%. No explanation is given
nor any reason why they think it is a bottleneck which caused this and not the founder
effect. Personally we think it might be both as there was a famine around that time too
and this might in turn have led the founders away from the larger population.
Slide 8
The researchers from this article divided their 20 minimal haplotypes in 6
geographical regions from which the donor had family roots in that area. The most
common haplotype was found in 25.6% of the samples.
Black: most common haplotype.
Low GD in Savo for minimal and 16-loci.
This shows the reduced local male gene pool.
Slide 9
What are the dangers for the DNA analysis of Finnish forensic cases? We think it is
quite obvious from the number of common haplotypes I showed you. Applying a
general population database in forensic & paternity testing cases especially in the
regions shown in the diagram would be a big big mistake.