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Searching for the family roots using DNA research |
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As from the end of 2010, the genealogical research on the Recourt and related Belgian/Dutch family members is extended using DNA research. The current focus is on the Y –chromosome, which is passed on from father to son. Occasionally, a small part of the Y-chromosomal DNA changes being a point mutation (SNP=Single Nucleotide Polymorphism) or a duplication of a small DNA element (STR=Single Tandem Repeat). The recording of these small DNA variations within a human population allow the study of migration patterns, but also of presumed family relations. Are you interested to know whether a biological relation exists between you and the Recourt family, please contact me at info(at)roucourt.eu |
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This page is under construction. For ongoing DNA results, please visit the blog at www.rouchout.blogspot.com |
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DNA research
Since the sequencing of the first human genome was completed at the start of this millennium, molecular genetic research has accelerated. Current and future developments using Next Generation Sequencing technologies will even further increase the (unforeseeable) potential of unravelling the secrets of the human genome. DNA technologies are already successfully used for diagnostic- and therapeutic medical applications, a field which will undoubtedly further develop during the coming decades.
For genealogy purposes, DNA analysing technologies are a very useful tool to further understand the origin of individuals and populations. To study the origin of the paternal line, it should be realized that the father’s sex chromosome Y is only passed to male childs. For studying maternal origins, it should be realized that mitochondrial DNA is passed on from the mother to her children (see figures). Therefore, both Y chromosomal and mitochondrial DNA analyses can reveal the origin of an individual or a genetically-linked population. |
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Left: Male inheritance of the Y chromosome.
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Y chromosome, SNPs and STRs
The humane genome is dispersed on 46 chromosomes from which 44 are arranged in pairs of two. In addition, a female has two X chromosomes while a man has one X and one Y chromosome. Each chromosome contains a long DNA helix which codes for genes enabling us to develop and function. The basic building blocks of the DNA are four types of base pairs: A-T, T-A, G-C and G-C. A set of three base pairs is called a “codon” which encodes a specific amino acid, the basic building block of a protein. A set of codons forms a functional gene. In principal, there is very little variation in the gene codes, since alterations (“mutations”), for instance from A to T, may result in a non-functional gene. Mutations in non-coding regions between genes may however have no impact on the genotype and resulting phenotype. It are those regions which appear to have changed between individual humans without rendering an evolutionary benefit. These neutral alterations can be used in genealogy and population genetics. Alterations in the Y-chromosome will render information of the origin and relationships of paternal lines. In principle two kinds of neutral Y chromosome alterations can be discriminated:
- SNPs or Single Nucleotide Polymorphisms. These are unique non-frequent mutations which occur at a single point of the Y chromosome. For instance a T is altered in an A, and subsequently all male generations thereafter which have an A base instead of a T base. Most specific point mutations appear rare during human evolution.
- STRs or Single Tandem Repeats. The Y chromosomes contains non-functional repetitive DNA sequences. These sequences may duplicate further during evolution, thereby increasing the number of repeating units. A DYS (DNA Y-chromosome Segment) value may for instance increase from 10 (father) to 11 copies (son). Apparently, fast– and slow multiplying STRs can be discriminated. |
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Top left: basic architecture of a chromosome containing a helical DNA molecule. The four basic building blocks are: A,T, G and C which form specific base pairs.
Middle left: Position of a number of Single Tandem Repeats (STRs) at the male Y-chromosome. The DYS markers are numbered and contain a distinct value of repeating units. For instance DYS 391 (10): 10 copies of a repetitive unit at Y position 391. |
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