Question Inbreeding and DNA results

kike

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Valencia Spain
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sd
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Hi:
The question is: How can inbreeding affect the results on genetic ancestry? In a population with a strong mix of small groups of people who may be family, does it alter your outcomes in any way? How do chromosomes behave with these mixtures?

Un saludo y gracias.
 
There is no change in general. The main difference is, that people from inbred families or communities will share much more DNA with genealogical relatives and DNA matches than people from a non-inbred population. E.g., if you have cousins in your pedigree, and a relative from that branch of your family does a DNA test, he might share double the amount of DNA compared to a person which just has a single connection.
Otherwise it makes no fundamental difference.
 
No hay cambios en general. La principal diferencia es que las personas de familias o comunidades endogámicas compartirán mucho más ADN con parientes genealógicos y coincidencias de ADN que las personas de una población no endogámica. Por ejemplo, si tienes primos en tu pedigrí y un pariente de esa rama de tu familia se hace una prueba de ADN, podría compartir el doble de ADN en comparación con una persona que solo tiene una sola conexión.
De lo contrario, no hay ninguna diferencia fundamental.
Gracias y un saludo.
 
I think its how you create bottlenecks, and drift in terms of genetics looking from present.
Because intermixing create neighbour populations that are close to each other, and with inbreeding you isolate.
Island populations often show this
 
I think its how you create bottlenecks, and drift in terms of genetics looking from present.
Because intermixing create neighbour populations that are close to each other, and with inbreeding you isolate.
Island populations often show this

In reality, there are important issues. I have found some videos, also regarding chromosome fragmentation.


Un saludo

Enri
 
In reality, there are important issues. I have found some videos, also regarding chromosome fragmentation.


Un saludo

Enri

The video is quite educational, but they wrong on Ancestry's Timber algorithm, because it doesn't work well. It reduces and completely deletes matches which are real and vice versa. It sometimes works just fine, but due to reducing or even sorting out real, valuable matches, it causes more problems than it solves. Similarly, FTDNA and 23andMe have a better representation of the matches, even if you have to sort it out yourself, what's real and what's not.
Timber is just great in theory, not in practise.
She is also much too negative on small segments, since even though many are not real, many others are and some can point to actual, provable genealogical relatedness. I was able to verify segments as small as 3 cM in specific instances, yet alone 7-10 cM sized segments.

Of course, if you want to go for very high matches (90 cM and higher) only and have lots of matches, you don't have to care. But if you want to trace more distant relationships, then its not recommendable to rely on Timber and disregard small segments (< 20 cm).

However, for actual endogamous people, small segments can be oftentimes useless, yet even that depends and can't generalised for all cases.
 
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The video is quite educational, but they wrong on Ancestry's Timber algorithm, because it doesn't work well. It reduces and completely deletes matches which are real and vice versa. It sometimes works just fine, but due to reducing or even sorting out real, valuable matches, it causes more problems than it solves. Similarly, FTDNA and 23andMe have a better representation of the matches, even if you have to sort it out yourself, what's real and what's not.
Timber is just great in theory, not in practise.
She is also much too negative on small segments, since even though many are not real, many others are and some can point to actual, provable genealogical relatedness. I was able to verify segments as small as 3 cM in specific instances, yet alone 7-10 cM sized segments.

Of course, if you want to go for very high matches (90 cM and higher) only and have lots of matches, you don't have to care. But if you want to trace more distant relationships, then its not recommendable to rely on Timber and disregard small segments (< 20 cm).

However, for actual endogamous people, small segments can be oftentimes useless, yet even that depends and can't generalised for all cases.

True, I also think the same thing, I find that small segments do seem to indicate a direct relationship through other data such as surnames, obviously the large ones are very clear, but these are always from relatively close relatives. In any case, my interest in the topic of endogamy is related to results that DNA can give and its comparison with ancient samples of archaeological remains, not with current samples. Also, how does inbreeding affect the results of these samples, since inbreeding was much more normal in the past and also because some of my family lived in a relatively isolated area and some inbreeding may also have existed for some centuries and I am interested in how may affect comparisons
Thank you so much.
 
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