Abstract:The Afrikaner population of South Africa are the descendants of European colonists who started to colonize the Cape of Good Hope in the 1600’s. In the early days of the colony, mixed unions between European males and non-European females gave rise to admixed children who later became incorporated into either the Afrikaner or the “Coloured” populations of South Africa. Ancestry, social class, culture, sex ratio and geographic structure affected admixture patterns and caused different ancestry and admixture patt… Show more
“…On the other hand, the East African ancestry seems to be male-biased; with an X/A ratio of 0.42 ± 0.07 SD in the Hessequa descendants, 0.46 ± 0.09 SD in the Nama, 0.57 ± 0.13SD in the Khwe, 0.54 ± 0.23 SD in the ǂKhomani and 0.83 ± 0.23 SD in the Coloured population of Wellington. Similarly, we also see male-driven admixture for the European ancestry, as expected [ 55 ], with X/A averages ranging between 0.50 and 0.93. Fig.…”
Background
Hunter-gatherer lifestyles dominated the southern African landscape up to ~ 2000 years ago, when herding and farming groups started to arrive in the area. First, herding and livestock, likely of East African origin, appeared in southern Africa, preceding the arrival of the large-scale Bantu-speaking agro-pastoralist expansion that introduced West African-related genetic ancestry into the area. Present-day Khoekhoe-speaking Namaqua (or Nama in short) pastoralists show high proportions of East African admixture, linking the East African ancestry with Khoekhoe herders. Most other historical Khoekhoe populations have, however, disappeared over the last few centuries and their contribution to the genetic structure of present-day populations is not well understood. In our study, we analyzed genome-wide autosomal and full mitochondrial data from a population who trace their ancestry to the Khoekhoe-speaking Hessequa herders from the southern Cape region of what is now South Africa.
Results
We generated genome-wide data from 162 individuals and mitochondrial DNA data of a subset of 87 individuals, sampled in the Western Cape Province, South Africa, where the Hessequa population once lived. Using available comparative data from Khoe-speaking and related groups, we aligned genetic date estimates and admixture proportions to the archaeological proposed dates and routes for the arrival of the East African pastoralists in southern Africa. We identified several Afro-Asiatic-speaking pastoralist groups from Ethiopia and Tanzania who share high affinities with the East African ancestry present in southern Africa. We also found that the East African pastoralist expansion was heavily male-biased, akin to a pastoralist migration previously observed on the genetic level in ancient Europe, by which Pontic-Caspian Steppe pastoralist groups represented by the Yamnaya culture spread across the Eurasian continent during the late Neolithic/Bronze Age.
Conclusion
We propose that pastoralism in southern Africa arrived through male-biased migration of an East African Afro-Asiatic-related group(s) who introduced new subsistence and livestock practices to local southern African hunter-gatherers. Our results add to the understanding of historical human migration and mobility in Africa, connected to the spread of food-producing and livestock practices.
“…On the other hand, the East African ancestry seems to be male-biased; with an X/A ratio of 0.42 ± 0.07 SD in the Hessequa descendants, 0.46 ± 0.09 SD in the Nama, 0.57 ± 0.13SD in the Khwe, 0.54 ± 0.23 SD in the ǂKhomani and 0.83 ± 0.23 SD in the Coloured population of Wellington. Similarly, we also see male-driven admixture for the European ancestry, as expected [ 55 ], with X/A averages ranging between 0.50 and 0.93. Fig.…”
Background
Hunter-gatherer lifestyles dominated the southern African landscape up to ~ 2000 years ago, when herding and farming groups started to arrive in the area. First, herding and livestock, likely of East African origin, appeared in southern Africa, preceding the arrival of the large-scale Bantu-speaking agro-pastoralist expansion that introduced West African-related genetic ancestry into the area. Present-day Khoekhoe-speaking Namaqua (or Nama in short) pastoralists show high proportions of East African admixture, linking the East African ancestry with Khoekhoe herders. Most other historical Khoekhoe populations have, however, disappeared over the last few centuries and their contribution to the genetic structure of present-day populations is not well understood. In our study, we analyzed genome-wide autosomal and full mitochondrial data from a population who trace their ancestry to the Khoekhoe-speaking Hessequa herders from the southern Cape region of what is now South Africa.
Results
We generated genome-wide data from 162 individuals and mitochondrial DNA data of a subset of 87 individuals, sampled in the Western Cape Province, South Africa, where the Hessequa population once lived. Using available comparative data from Khoe-speaking and related groups, we aligned genetic date estimates and admixture proportions to the archaeological proposed dates and routes for the arrival of the East African pastoralists in southern Africa. We identified several Afro-Asiatic-speaking pastoralist groups from Ethiopia and Tanzania who share high affinities with the East African ancestry present in southern Africa. We also found that the East African pastoralist expansion was heavily male-biased, akin to a pastoralist migration previously observed on the genetic level in ancient Europe, by which Pontic-Caspian Steppe pastoralist groups represented by the Yamnaya culture spread across the Eurasian continent during the late Neolithic/Bronze Age.
Conclusion
We propose that pastoralism in southern Africa arrived through male-biased migration of an East African Afro-Asiatic-related group(s) who introduced new subsistence and livestock practices to local southern African hunter-gatherers. Our results add to the understanding of historical human migration and mobility in Africa, connected to the spread of food-producing and livestock practices.
“…The absence of CNVs in the White Afrikaner population with its European heritage is surprising, as many CNVs (including a founder variant reported for the Netherlands [62]) have been reported for this region of the world. Investigators genotyped a large subset (n = 7746) of Afrikaner individuals using ~5 million genome-wide markers to determine parental source populations worldwide [63]. The authors confirmed that ~95.3% of Afrikaner ancestry came from mostly northwestern European populations, with the remaining section contributed by admixture with slaves and the local Khoe-San groups [63].…”
Section: Discussionmentioning
confidence: 93%
“…Investigators genotyped a large subset (n = 7746) of Afrikaner individuals using ~5 million genome-wide markers to determine parental source populations worldwide [63]. The authors confirmed that ~95.3% of Afrikaner ancestry came from mostly northwestern European populations, with the remaining section contributed by admixture with slaves and the local Khoe-San groups [63].…”
Background
Pathogenic variants that occur in the familial breast cancer genes (BRCA1/2) lead to truncated ineffective proteins in the majority of cases. These variants are mostly represented by small deletions/insertions, nonsense- and splice-site variants, although some larger pathogenic rearrangements occur. Currently, their contribution to familial breast cancer (BC) and ovarian cancer (OVC) in South Africa (SA) is unknown.
Methods
Seven hundred and forty-four patients affected with BC or OVC were screened for larger genomic rearrangements (LGRs) by means of multiplex ligation-dependent probe amplification or Next Generation Sequencing using the Oncomine™ BRCA research assay.
Results
The patients represented mostly medium to high-risk families, but also included lower risk patients without a family history of the disease, diagnosed at an early age of onset (< 40 years). Eight LGRs were detected (1.1%); seven in BRCA1 with a single whole gene deletion (WGD) detected for BRCA2. These eight LGRs accounted for 8.7% of the 92 BRCA1/2 pathogenic variants identified in the 744 cases. The pathogenic LGRs ranged from WGDs to the duplication of a single exon.
Conclusions
Larger rearrangements in BRCA1/2 contributed to the overall mutational burden of familial BC and OVC in SA. Almost a quarter of all pathogenic variants in BRCA1 were LGRs (7/30, 23%). The spectrum observed included two WGDs, one each for BRCA1 and BRCA2.
“…19 Founder effects for a number of diseases have been observed in this population, possibly due to the fact that the disease alleles were present in the original progenitors and were later amplified through exponential population expansion. 20 However, it is important to note that the fact that a disease is more common in some populations than in others does not mean it is exclusive to a particular population. The same genetic diseases can be found across all populations in the world.…”
The basics of DNA DNA stands for deoxyribonucleic acid. Everyone, with the exception of identical twins, has a unique set of DNA. This DNA is an instruction manual that contains the information our cells need to make proteins and other molecules essential for our development, growth and survival. All human cells, except red blood cells, contain DNA, which is stored in a part of the cell known as the nucleus. DNA occurs in the form of a double helix, which resembles a twisted ladder-like structure. The rungs of this 'ladder' are made up of four nucleotide bases: adenine (A), cytosine (C), guanine (G) and thymine (T). Combinations of these bases form three-letter 'words' called codons, which the cell reads to make proteins. Each codon specifies which protein building block, known as an amino acid, should be added next during the process of making proteins. Various combinations of amino acids make up different proteins. The three-letter codons are pieced together in an estimated 20 000 to 25 000 'sentences' called genes. 2 The genes are separated by nucleotide bases which do not code for amino acids but are still important. These stretches of jumbled-up bases are called non-coding DNA (also referred to as junk DNA) and they make up the vast majority (98.8%) of our DNA. Some of the non-coding DNA functions as 'punctuation marks', providing information as to where one gene ends and the next one starts. Other non-coding DNA regulates when and how much of the proteins are made, or control how DNA is packaged within the cell. However, there is still a lot that is not yet known about non-coding DNA and its functions.
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