Determining Human Races.

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curious
curious's picture
Determining Human Races.

I am not a scientist, but i need some help on a few questions relating to genetics. If you could help, it would be great.

Can you determine which group of people you come from with DNA? e.g. Are Maltese Italians?

If there are certain frequencies in Y-DNA, would they be the same in mt-DNA? I have seen a study on human races and it was based on Y-DNA. If it indicated the men in that population originated from a certain group of people, surely the women of that population would be the same. Would you get the same results on mt-DNA given it is the same people being tested?

What distinguishes the origins of that population? Is it the base sequences? Or is it the frequency of similar alleles?

How accurate are these DNA tests?

If you test the Y-DNA only, is it enough for the results to be valid? Surely the mt-DNA would not differ much from the Y-DNA.

I am refering to this study:

http://web.archive.org/web/20030715040756/www.racearchives.com/calc/haplo_profiles.asp?dbname=ychroms&popid=20

ryan_m
ryan_m's picture
Mitochondrial DNA is passed

Mitochondrial DNA is passed from mother to daughter whereas the Y chromosome is passed from father to son. All other chromosomes undergo what is called 'crossing over' which results in shuffling between mom and dad copies every generation. This is why only MT and Y are used for these types of studies. The signal of ancient heritage gets 'mixed up' in all the other chromosomes too quickly to give information on ancient heritage.

If it is information on "race" then there is no clear cut answer from DNA anyway, since "race" is an illusion anyway. We are all related and come from the same place and a small founder population originally.

curious
curious's picture
ryan_m wrote:Mitochondrial

ryan_m wrote:

Mitochondrial DNA is passed from mother to daughter whereas the Y chromosome is passed from father to son. All other chromosomes undergo what is called 'crossing over' which results in shuffling between mom and dad copies every generation. This is why only MT and Y are used for these types of studies. The signal of ancient heritage gets 'mixed up' in all the other chromosomes too quickly to give information on ancient heritage.

If it is information on "race" then there is no clear cut answer from DNA anyway, since "race" is an illusion anyway. We are all related and come from the same place and a small founder population originally.

Thanks for the reply, ryan_m.

But wouldn't the Asian, African, Indo-European races etc etc develop there own DNA characteristics over time to eventually be distinguishable from other races, however small they may be?

Would there be a signal of ancient heritage or race in the Mitochondral and Y chromosomes, seeing as they are the only ones that dont get mixed up? This study seems to show that you can make these connections.

Jason King
Jason King's picture
There are certain features

There are certain features that can be associated with groups of a given ethnicity. The best characterised are probably the mutations that make carriers more susceptible to a particular disease or condition or situations in which a gene product is not expressed. (I'd have to check but the lower alcohol tolerances associated with far Eastern ethnicities may be one case in point).

Over time, one would not expect people to become more similar as you suggest. Rather the opposite, either through mixing between ethnic groups or simple mixing of parental genes within a group.

However, as a result of some very significant environmental change, some groups may be better able to adapt as a result of their genetic makeup and over time Darwin would have expected this to result in a greater proportion of the population carrying this / these genes.

Studies in the UK have been very successful in tracking the spread of the Vikings from Scandanavia to the north of Scotland round to Ireland and parts of the western coast of England. These studies analysed the Y-chromasome. (...although you don't need any genetic techniques to realise that the Vikings came to Scotland since about 12% of the population have red hair!)

ryan_m
ryan_m's picture
curious wrote:ryan_m wrote

curious wrote:

ryan_m wrote:
Mitochondrial DNA is passed from mother to daughter whereas the Y chromosome is passed from father to son. All other chromosomes undergo what is called 'crossing over' which results in shuffling between mom and dad copies every generation. This is why only MT and Y are used for these types of studies. The signal of ancient heritage gets 'mixed up' in all the other chromosomes too quickly to give information on ancient heritage.

If it is information on "race" then there is no clear cut answer from DNA anyway, since "race" is an illusion anyway. We are all related and come from the same place and a small founder population originally.

Thanks for the reply, ryan_m.

But wouldn't the Asian, African, Indo-European races etc etc develop there own DNA characteristics over time to eventually be distinguishable from other races, however small they may be?

Would there be a signal of ancient heritage or race in the Mitochondral and Y chromosomes, seeing as they are the only ones that dont get mixed up? This study seems to show that you can make these connections.

You seem to be very fixated on the question of defining race based on genetic characteristics. Please understand that the concept of race is much older than that, so races become less defined when the complexity of the genome is considered. All humans are related and share more than 99% of the same genome sequence. A particular family contains only a subset of the variability found across all humans, and a 'race' would contain a larger subset of that variability. There is no scientific line that follows the concept of race. Some haplotype blocks are generally specific to certain races, as are some diseases, but no one mutation/genotype/genomic feature will define a particular race. There is not really a scientific application for this anyway, only a whole pandora's box of ethical considerations, so why bother?

Ryan

bluegenes
bluegenes's picture
Below is a link to a website

Below is a link to a website that offers the DNA Heritage testing that you originally asked about. "Family Tree DNA" tests both the Y-DNA and mtDNA. Based on the information they provide, they use the Y Chromosome, which is transmitted from father to son, to test various markers that help trace the direct male lineage. Mutations are small changes that occur in the DNA at random intervals, and occur an average of once for every 500 generations per marker - this information can be useful in family tree identification. Markers are classified as STR (short tandem repeats) because at each marker location, a short DNA code repeats itself. The allele value is the number of times this code is repeated at that particular marker. A haplotype is the result of a the string of allele values gathered from the Y-DNA test. Using the various haplotypes gathered from the test, this particular company also offers to estimate the "haplogroup" which is the major population group, and offers insight into the ancient origin of the male line. As Ryan_m stated earlier, we all come from the same small "founder group" population, and this test can help track which haplotype block your lineage comes from.

Family Tree DNA uses the mtDNA (passed from mother to child, and found in the mithochondria) to test the direct maternal line. This DNA mutates at a MUCH slower rate than the Y-DNA, so it can ultimately be used to determine your "world origin". THis is because the female lines are distinguishable from eachother due to the sequence of mutations that have built up in a certain lineage over thousands of years. The results of the mtDNA are compared to the CRS (Cambridge Reference Sequence) to identify your haplogroup (which indicates which continent you most likely originated from, and possibly even which region). Hope this helps : )

http://www.ftdna.com/tutorial_A.html

curious
curious's picture
Thanks all, for the

Thanks all, for the information and links.

It seems that there are some cases in which certain characteristics can be defined to a particular group like the Vikings example mentioned.

I just find it interesting to see if it is possible to determine whether a current day race is related to an ancient race. Whther they are the original inhabitants or simply migrated there and have originated from another race/area.

ethund
ethund's picture
curious wrote:I am not a

curious wrote:

I am not a scientist, but i need some help on a few questions relating to genetics. If you could help, it would be great. Can you determine which group of people you come from with DNA? e.g. Are Maltese Italians? If there are certain frequencies in Y-DNA, would they be the same in mt-DNA? I have seen a study on human races and it was based on Y-DNA. If it indicated the men in that population originated from a certain group of people, surely the women of that population would be the same. Would you get the same results on mt-DNA given it is the same people being tested? What distinguishes the origins of that population? Is it the base sequences? Or is it the frequency of similar alleles? How accurate are these DNA tests? If you test the Y-DNA only, is it enough for the results to be valid? Surely the mt-DNA would not differ much from the Y-DNA. I am refering to this study: http://web.archive.org/web/20030715040756/www.racearchives.com/calc/haplo_profiles.asp?dbname=ychroms&popid=20

With a number of so called "ancestry informative markers" (AIM), it is possible to test the proportion of a specific ancestral group in your genes.  For example, an African American may have 80% from the African ancestry and 20% from the European ancestry.  To do such a test, you need to make the assumption of which and how many ancestral groups you are from.

Ivan Delgado
Ivan Delgado's picture
Hi Curious, 

Hi Curious, 
As a Geneticist I could not help but provide my two cents. The idea of race comes from the observation that as a populations splits and evolve as distinct groups/populations, genetic variations accumulate that are distinct in each case (as their genomes adapt to their particular environments) . Yet, as you can imagine, the more these populations intermingle, as it happens more and more these days, the concept of race gets "diluted" as these genetic variations are shared between populations. 
One of the neat things about this fact, I think, is that you can find genetic variants that are shared by all populations (I prefer the term population than race), and others that are only shared by a few populations. The more these variants are shared across populations, the older this variant is, and the fewer populations that share a given variant, the later this variant developed. So for example there are variants in populations in Africa that are shared by everyone in the world, while there are variants in populations in Europe that are only found in those populations; this is one of the reasons why we believe man originated in Africa and then migrated to the other parts of the world. 
A very good resource on this information is the Genographic project run by National Geographic. The link is here:
https://genographic.nationalgeographic.com/genographic/index.html
Happy Darwin's 200th Anniversary