Table 1.

α⁺ and β^S frequencies in South Asian populations

This table has been compiled from the literature and from some extra sequencing done in preparation for this article. We included only estimates from the literature where the sample size was at least 15, so three of the tribal groups studied by Fodde et al. in their 1991 paper have been left out (the Kolam, the Kotiya, and the Nooka Dora). We also left out the Konda Kammari (from the same paper), because we could find no source for a β^S frequency in that group. α⁺ refers to any mutation that eliminates alpha globin production from one of the two alpha globin genes on chromosome 16. Deletions that eliminate alpha globin production from both genes exist (these are usually referred to as α⁰ deletions), but were not reported in any of these specific populations. The vast majority of α⁺ worldwide is caused by either the –α^3.7 deletion (a result of unequal crossing over between two homologous sections of the chromosome which are 3.7 kb apart) or the –α^4.2 deletion (a result of unequal crossing over between two homologous sections of the chromosome which are 4.2 kb apart). The 3.7 deletion can be categorized into types I, II, and III depending upon where in the homologous stretch of DNA the crossover occurred. Globally, type I is the most common and type III the rarest. The “other” column in the table notes unusual nondeletional alpha thalassaemic variants such as Haemoglobin Koya Dora (HbKD) and Hb Rampa, or other abnormalities such as the triplication of the alpha globin gene (the other product of unequal crossing over). When an α⁺ and a β^S frequency estimate appear in the same row, they were estimated from the same population in the same study. In all other cases, we have had to resort to different studies of the same ethnic group in the same area

		Frequency of α+
Location	Tribal group	–α3.7 deletion	–α4.2 deletion	Others	Total	Frequency of βS	Sources	Number typed
Sundargarh district of Orissa	Munda	0.5			unknown (4.2 frequency yet to be established)	0; 0.016	This article (see Supporting information for genotyping methods) Balgir et al. (2006a) for second βS estimate	44 (this article); 96 (Balgir et al. 2006a)
	Oraon	0.625				0; 0	This article, Balgir et al. (2006a)	36 (this article); 104 (Balgir et al. 2006a)
Central Terai (Nepal)	Tharu	0.83 (type I)	0	None noted	0.83	0	Modiano et al. 1991	18 (α+); 124 (βS)
Western Terai (Nepal)	Tharu	0.67 (type I), 0.05 (type II)	0	None noted	0.72	0.05	Modiano et al. 1991	18 (α+); 185 (βS)
Western Terai (India)	Tharu	0.94				0.1	Sinha et al. 2009 (α+), this article (βS)	53
Andhra Pradesh (AP)	Koya Dora	0.26 (type I) 0.1 (type II)	0.32;	0.12 (HbKD)	0.8	0.12	Fodde et al. 1988;	25
		0.3 (type I) 0.07 (type II)	0.33	0.07 (HbKD); 0.07 (Hb Rampa)	0.77		Fodde et al. 1991	30
						0.088	Nayudu 1990	452
						0.0673	Babu et al. 2002	1099
	Valmiki	0.26 (type I)	0.08	None noted	0.46		Fodde et al. 1991	50
		0.12 (type II)				0.172	Nayudu 1990	553
						0.1216	Babu et al. 2002	950
	Konda Dora	0.18 (type I)	0.32	0.05	0.55		Fodde et al. 1991	22
				(HbKD)		0.0629	Babu et al. 2002	668
	Konda Reddi/Konda Reddy	0.531 (type I)	0	0.0625 (alpha globin triplication)	0.531	0.03	Fodde et al. 1988;	16
		0.35 (type I)	0		0.35		Fodde et al. 1991	17
						0.0696	Nayudu 1990	632
						0.0635	Babu et al. 2002	724
	Bhaghatha/Bagatha	0.44 (type I)	0.26	None noted	0.6		Fodde et al. 1991	27
						0.0618	Babu et al. 2002	283