Heterogeneity and diversity of ABO and Rh blood group genes in select Saudi Arabian populations

Abstract

In order to investigate the diversity of ABO and Rh blood group genes in the Saudi Arabian population, we assembled the phenotypic data of approximately 66,000 subjects from ten representative Saudi populations: Al-Khobar, Riyadh, Tabuk/Madina Al-Munawaara, Jeddah, Abha, South region, Sakaka, Domah, Al-Qurayat, and Sweer. The frequencies of p[A], q[B], and r[O] alleles at the ABO locus were observed to be 0.1688, 0.1242, and 0.7070, respectively, and the frequency of the D allele at the Rh locus was 0.7138. The heterozygosities at the ABO and Rh loci were 0.4563 and 0.4086, respectively, while the combined heterozygosity was 0.4324. Homogeneity tests revealed the population of Abha to be the most heterogeneous while that of Tabuk/Madina was found to be the least heterogeneous. Homogeneity was higher among the Northern populations while Southern populations demonstrated subdivisions and stratification. Gene diversity analyses yielded a total heterozygosity value of 0.4449. The coefficient of gene differentiation was 0.0090. Nei’s genetic distance analyses showed that there was close affinity between the populations of Al-Khobar and Riyadh. The largest differences were observed between the populations of Sakaka and Domah. Furthermore, negative correlations were found between p[A] and r[O] alleles, and between q[B] and r[O] alleles at the ABO locus. Clinal analyses revealed that the r[O] allele showed an increasing trend from North-East to South-West, and conversely the q[B] allele exhibited a decreasing trend at these coordinates. These analyses present interesting aspects of the blood group allele distribution across the geography of Saudi Arabia.

Full text

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Genetics and Molecular Research 14 (3): 7850-7863 (2015)
Heterogeneity and diversity of ABO and Rh
blood group genes in select Saudi Arabian
populations
E.S. AlSuhaibani1, N.A. Kizilbash2 and S. Malik3
1Department of Zoology, College of Science, King Saud University,
Riyadh, Saudi Arabia
2Department of Biochemistry, Faculty of Medicine and Applied Medical Sciences,
Northern Border University, Arar, Saudi Arabia
3Human Genetics Program, Department of Animal Sciences,
Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, Pakistan
Corresponding authors: S. Malik
E-mail: malik@qau.edu.pk / fsd707@gmail.com
Genet. Mol. Res.14 (3): 7850-7863 (2015)
Received November 10, 2014
Accepted April 6, 2015
Published July 14, 2015
DOI http://dx.doi.org/10.4238/2015.July.14.11
ABSTRACT. In order to investigate the diversity of ABO and Rh
blood group genes in the Saudi Arabian population, we assembled the
phenotypic data of approximately 66,000 subjects from ten representative
Saudi populations: Al-Khobar, Riyadh, Tabuk/Madina Al-Munawaara,
Jeddah, Abha, South region, Sakaka, Domah, Al-Qurayat, and Sweer.
The frequencies of p[A], q[B], and r[O] alleles at the ABO locus were
observed to be 0.1688, 0.1242, and 0.7070, respectively, and the
frequency of the D allele at the Rh locus was 0.7138. The heterozygosities
at the ABO and Rh loci were 0.4563 and 0.4086, respectively, while the
combined heterozygosity was 0.4324. Homogeneity tests revealed the
population of Abha to be the most heterogeneous while that of Tabuk/
Madina was found to be the least heterogeneous. Homogeneity was
higher among the Northern populations while Southern populations
demonstrated subdivisions and stratication. Gene diversity analyses

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yielded a total heterozygosity value of 0.4449. The coefcient of gene
differentiation was 0.0090. Nei’s genetic distance analyses showed
that there was close afnity between the populations of Al-Khobar and
Riyadh. The largest differences were observed between the populations
of Sakaka and Domah. Furthermore, negative correlations were found
between p[A] and r[O] alleles, and between q[B] and r[O] alleles at
the ABO locus. Clinal analyses revealed that the r[O] allele showed
an increasing trend from North-East to South-West, and conversely
the q[B] allele exhibited a decreasing trend at these coordinates. These
analyses present interesting aspects of the blood group allele distribution
across the geography of Saudi Arabia.
Key words: Saudi population; Genetic heterogeneity; Gene diversity;
ABO; Rh; Blood groups
INTRODUCTION
Genetic studies regarding the populations of Saudi Arabia are rare. There are several
preliminary reports available on the ABO and Rh blood group polymorphisms in Saudi sub-
populations. Bashwari et al. (2001) reported blood group phenotypic data from the Eastern
region of Saudi Arabia and showed that blood type “O” was the most common. Al-Himaidi
and Umar (2002) generated a phenotypic record of Saudi citizens originating from various
regions. The authors presented the distribution of phenotypic proportions of blood types but
allelic frequencies and heterozygosities at the ABO and Rh loci were not mentioned. Sarhan
et al. (2009) also observed the blood group proportions in the Southwestern Saudi population.
Eweidah et al. (2011) attempted to report the distribution of blood groups in four cities of the
Al-Jouf region in the North of Saudi Arabia. Overall, these studies present a disjointed picture
of the distribution of blood group polymorphisms in Saudi Arabia.
Most of the previous studies employing molecular markers in Saudi populations have
presented regional data and incorporated small sample sizes. An early study by Sinha et al.
(1999) examined eight short tandem repeats in Saudi populations. Recent studies have em-
ployed molecular makers in order to observe the diversity in the Saudi population. Alanazi
et al. (2013) explored selected polymorphisms in DNA repair genes in the population of the
central region of Saudi Arabia and observed a unique pattern of alleles in that population. In
another study, Mustafa et al. (2014) carried out molecular genotyping of the Rh locus and
observed the RHD and RHCE variants in Turabah Province. For the RHD variant, 86.5% sub-
jects were found to be RHD positive and 13.5% were RHD negative; the most common phe-
notype was DcE4+. Abu-Amero et al. (2013) studied four single nucleotide polymorphisms
in two genes, TLR2 and TLR4, and genotyped 201 unrelated Saudi individuals. The authors
concluded that regional variation at these loci could have been shaped by both evolutionary
pressures and bidirectional human migrations.
The most frequently studied genetic makers in the Saudi populations are the ABO and
Rh blood group loci (Bashwari et al., 2001; Al-Himaidi and Umar, 2002). In order to appreci-
ate the diversity of these markers across the geography of Saudi Arabia, we have carried out a
detailed study and have investigated genetic heterogeneity and gene diversity at the ABO and
Rh loci in the representative Saudi populations.

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MATERIAL AND METHODS
Subjects
Blood group phenotypic data of >66,000 subjects from ten representative Saudi popu-
lations were assembled from publically available reports (Table 1) (Bashwari et al., 2001; Al-
Himaidi and Umar, 2002; Sarhan et al., 2009; Eweidah et al., 2011). The Eastern province was
represented by Al-Khobar; the middle province was represented by Riyadh, the North-Western
region by Tabuk/Madina Al-Munawaara, the Western region by Jeddah, the South-West by
Abha, and the Northern region was represented by Sakaka, Domah, Al-Qurayat, and Sweer
cities (Figure 1). Only records with sample sizes ≥100 were considered.
There were few popu-
lations for which multiple data sets were available in the published literature. Only the most
recent records or data with the largest sample size were retained (
Bashwari
et al., 2001).
Tribe-specic data were not included in this study. Blood group data for cohorts of diseased/
morbid subjects were not included in the analyses. Data from adjoining populations, such as
Bahrain, United Arab Emirates, and Yemen, were also not included in this study.
Population Sample (N) Phenotype (%) Reference
A B AB O Rh+ Rh-
Al-Khobar 57,396 26.43 18.44 4.07 51.07 92.10 7.90 Bashwari et al. (2001)
Riyadh 3324 25.99 20.01 4.00 50.00 92.00 8.00 Bashwari et al. (2001)
Jeddah 3924 27.01 16.00 3.49 53.49 92.00 8.00 Albaz (2001)
South region 291 33.68 11.34 2.75 52.23 89.69 10.31 Al-Himaidi and Umar (2002)
Abha 944 33.37 6.04 3.81 56.78 92.80 7.20 Sarhan et al. (2009)
Tabuk/Madina Al-Munawaara 166 30.12 12.05 4.82 53.01 92.17 7.83 Ozsoylu and Alhejaili (1987)
Sakaka 100 23.00 24.00 5.00 48.00 86.00 14.00 Eweidah et al. (2011)
Domah 100 29.00 30.00 6.00 35.00 94.00 6.00 Eweidah et al. (2011)
Al-Qurayat 100 29.00 22.00 9.00 40.00 92.00 8.00 Eweidah et al. (2011)
Sweer 100 29.00 26.00 9.00 36.00 93.00 7.00 Eweidah et al. (2011)
Total* 66,445 26.70 19.09 4.21 50.00 91.81 8.19
*Proportions in total Saudi population were based on data from 25 sub-populations.
Table 1. ABO and Rh blood group proportions in ten Saudi Arabian populations.
Descriptive analyses of the phenotypic data were performed and blood groups were
presented as percentages (Gerstman, 2008). Allele frequencies were calculated at the ABO
locus using the maximum likelihood method (Mather, 1964). The frequency of the Rh(d) allele
was calculated from the square-root of the frequency of Rh(-) phenotypes. Prior to the analy-
ses, Hardy-Weinberg equilibrium (HWE) was checked through goodness-of-t tests (Silva,
2002; Malik and Amin-ud-Din, 2013). Heterozygosity at the individual ABO and Rh loci and
the combined heterozygosities were calculated using the method of Nei (1987).
To observe the variability at the blood group systems, coefcients of variance (CoV)
were calculated across the phenotypic and allelic estimates. Homogeneity was tested between
the populations (Neel and Schull, 1954). The Z-test was employed to check the signicance of
the heterogeneity of blood group proportions among the studied populations (Gerstman, 2008).
Homogeneity tests for allele frequencies were carried out to establish an eloquent grouping of
studied populations (Neel and Schull, 1954). MS Excel (Microsoft, Redmond, WA, USA) and
GraphPad Prism (ver. 5) (San Diego, CA, USA) were used for graphical presentations.

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The degree of differentiation according to both blood group/polymorphic systems was
estimated for all populations (Nei, 1987). Nei’s genetic alignment distances (DA) were calcu-
lated using the allelic frequencies (Nei and Roychoudhury, 1982). The resulting matrices were
displayed by UPGMA dendrogram (Sneath and Sokal, 1973; Ota, 1993).
RESULTS
Blood group proportions and allele frequencies
For the overall Saudi population, the blood type “O” was the most common for the
ABO system (50.0%), followed by types “A” (26.70%), “B” (19.09%), and “AB” (4.21%)
(Table 1). For the Rhesus system, the Rh+ blood group was found in 91.81% subjects while
8.19% subjects were Rh-. Among the regional samples, type “O” was highest in Abha (56.78%)
and lowest in Domah (35%); type “A” was highest in the South region (33.68%) and lowest
in Sakaka (23%); type “B” was highest in Domah (30%) and lowest in Abha (6.04%); and
type “AB” was observed to be highest in Al-Qurayat and Sweer (9%) and lowest in the South
region (2.75%) (Table 1, Figures 2 and 3). For the Rhesus system, Rh+ was found to be highest
in Domah (94%) and lowest in Sakaka (86%).
Figure 1. Map of the Arabian Peninsula showing the populations of Saudi Arabia employed in the present study.

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Figure 3. Box and whisker plots demonstrating the ranges of blood type proportions in Saudi populations.
Figure 2. Three-dimensional area chart depicting the spread of blood group proportions in Saudi populations.
Blood type “AB” clearly shows the least variability while types “B” and “O” depict high variability.
Accordingly, the frequencies of p[A], q[B], and r[O] alleles at the ABO locus were
observed to be 0.1688, 0.1242, and 0.7070, respectively (Table 2). The frequencies of the
D and d alleles at the Rh locus were calculated to be 0.7138 and 0.2862, respectively. The
distributions of allele frequencies at the ABO and Rh loci were found to be highly variable in
the Saudi populations. For instance, the A[p] allele ranged from 0.1513-0.2119, B[q] between
0.0502-0.2015, and O[r] between 0.5949-0.7435 (Table 2 and Figure 4). At the Rh locus, the

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D allele revealed highest estimates in Domah (0.7551), and lowest in Sakaka (0.6258). The
samples were checked for conformity with HWE assumptions at the ABO locus. These analy-
ses established that most of the samples of Saudi populations were in conformity with HWE,
with the exception of Abha, which exhibited signicant deviation (c2 = 18.32; P < 0.001). The
total sample of Saudi population was consistent with HWE (Table 2).
Population ABO locus HWE test statistics; Rh locus
P value
p[A] q[B] r[O] Rh+ (D) Rh- (d)
Al-Khobar 0.1662 0.1197 0.7141 1.58 0.7189 0.2811
Riyadh 0.1634 0.1283 0.7082 0.41 0.7171 0.2829
Jeddah 0.1663 0.1027 0.7309 0.08 0.7171 0.2829
South region 0.2028 0.0732 0.7240 0.06 0.6789 0.3211
Abha 0.2062 0.0502 0.7435 18.32* 0.7316 0.2684
Tabuk/Madina Al-Munawaara 0.1925 0.0878 0.7197 1.38 0.7202 0.2798
Sakaka 0.1513 0.1573 0.6914 0.02 0.6258 0.3742
Domah 0.1952 0.2015 0.6034 0.69 0.7551 0.2449
Al-Qurayat 0.2111 0.1681 0.6208 0.78 0.7172 0.2828
Sweer 0.2119 0.1932 0.5949 0.13 0.7354 0.2646
Total# 0.1688 ± 0.0010 0.1242 ± 0.0009 0.7070 ± 0.0012 0.07 0.7138 ± 0.0017 0.2862 ± 0.0017
*Signicantly deviating from Hardy-Weinberg equilibrium (HWE) expectations. #Means ± SD.
Table 2. Distribution of allele frequencies at the ABO and Rh loci and Hardy-Weinberg equilibrium at the ABO locus.
Figure 4. Box and whisker plots depicting the ranges of allele frequencies at the ABO and Rh loci in Saudi
populations.
Locus heterozygosity
Heterozygosities at the individual ABO and Rh loci and combined blood group loci
were established in the Saudi populations. The heterozygosities at the ABO and Rh loci were

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0.4563 ± 0.0013 and 0.4086 ± 0.0010, respectively, and the combined heterozygosity was cal-
culated to be 0.4324 ± 0.0238 (Table 3). At the ABO locus, heterozygosity was observed to be
highest in Sweer (0.5667) and lowest in Abha (0.4024) (Figure 5). At the Rh locus, the highest
estimate was evident in Sakaka (0.4707) and lowest in Domah (0.3717) (Table 3). The dif-
ferences between populations became less remarkable when combined heterozygosities were
considered. The combined heterozygosity was highest in Sweer (0.4813 ± 0.0882) and lowest
in Abha (0.3979 ± 0.0047) (Figure 5).
Heterozygosity
Population ABO Rh Average
Al-Khobar 0.4481 0.4042 0.4261 ± 0.0220
Riyadh 0.4554 0.4058 0.4306 ± 0.0248
Jeddah 0.4276 0.4058 0.4168 ± 0.0109
South region 0.4301 0.4367 0.4342 ± 0.0033
Abha 0.4024 0.3929 0.3979 ± 0.0047
Tabuk/Madina Al-Munawaara 0.4386 0.4042 0.4227 ± 0.0172
Sakaka 0.4767 0.4707 0.4761 ± 0.0030
Domah 0.5600 0.3717 0.4682 ± 0.0946
Al-Qurayat 0.5445 0.4077 0.4785 ± 0.0688
Sweer 0.5667 0.3911 0.4813 ± 0.0882
Total# 0.4563 ± 0.0013 0.4086 ± 0.0010 0.4324 ± 0.0238
#Means ± SD.
Table 3. Heterozygosities at the studied loci in Saudi populations.
Figure 5. Comparison of individual and combined heterozygosities at the ABO and Rh loci in the studied populations
of Saudi Arabia.

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Variance at the phenotypic and allelic levels
In order to establish variability at the studied attributes, descriptive summaries were
generated for the phenotypic proportions and allelic frequencies (Figures 2-4). The CoV was
calculated to be the highest for the “AB” blood type (42.22%) followed by type “B” (39.60%),
while CoVs were 16.27 and 11.44% for the “O” and “A” blood types, respectively. At the ABO
allelic system, the q[B] allele depicted the highest CoV (39.86%), followed by p[A] and r[O]
alleles (12.12 and 8.23%, respectively) (Figure 5). At the Rh locus, the CoV at the d allele was
12.4% and at D it was 5.02%.
Heterogeneity among samples
Homogeneity was tested among the ten Saudi populations by employing the allelic
frequencies at the ABO locus and blood type proportions of the Rh system (Neel and Schull,
1954). Pairwise analysis for the ABO system demonstrated that the Abha population was the
most heterogeneous, while Sakaka exhibited the most homogeneity. However, for the Rh sys-
tem, Sakaka was the most heterogeneous sample. Z-tests were conducted through the pheno-
typic proportions and aggregated scores were used to compare the samples. The sample from
Abha appeared most heterogeneous followed by Sweer and Al-Qurayat. Furthermore, Tabuk/
Madina Al-Munawaara samples exhibited the least differences from the other populations. For
the phenotypic systems, differences were most obvious for the blood type “B”, followed by
types “O”, “AB”, and “A”.
Gene diversity analysis
To further establish gene differentiation among the Saudi populations the concept of
gene diversity was explored at the ABO and Rh loci. Expected heterozygosities were estimated
for the total population (HT) and within the subpopulations (HS). Absolute gene diversity (DST)
was calculated from the expected heterozygosities (Nei, 1987).
For the sake of convenience, Saudi population samples were pooled into two groups:
Southern and Northern. The Southern group comprised ve populations, Al-Khobar, Riyadh,
Jeddah, South region, and Abha ABO. The Northern region comprised Tabuk/Madina Al-Mu-
nawaara, Sakaka, Domah, Al-Qurayat, and Sweer (Table 4). Homogeneity was higher in the
Northern group compared to the Southern, which appeared subdivided and stratied. This was
evident from the behavior of “coefcient of inter-population gene differentiation” (GST) (Table
4). The DST at the pooled loci was almost four times higher in the Southern group compared to
the Northern. However, it was observed that HT was comparable with HS at both ABO and Rh
loci, which indicated only minor contributions of the inter-population components of genetic
differentiation. The total genetic diversity (HT) of the ABO locus was greater than that of the
Rh locus in both groups, as well as in the total pool. Taken together, across all populations DST
was 0.0040 and GST was 0.0090 (Table 4).
Genetic distance matrix through Nei’s genetic distance (DA) measures
Nei’s genetic distances (DA) were calculated for the recruited Saudi populations
(Table 5). There were high afnities between samples obtained from Al-Khobar and Riyadh,

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between Al-Khobar and Jeddah (DA = 0.0002), between Riyadh and Jeddah (DA = 0.0004),
between Jeddah and Tabuk/Madina Al-Munawara (DA = 0.0004), and between Domah and
Sweer (DA = 0.0005) (Table 5). Highest levels of heterogeneity (i.e., low afnities) were es-
tablished between Sakaka and Domah (DA = 0.0214), between South region and Domah (DA
= 0.0191), and between Abha and Domah (DA = 0.0177). Generally, the Domah population
demonstrated greater differences with other populations.
Population Locus HT HS DST GST
Northern group ABO 0.4339 0.4325 0.0014 0.0032
Rh 0.4095 0.4089 0.0006 0.0015
Pooled 0.4217 0.4207 0.0010 0.0024
Southern group ABO 0.5195 0.5149 0.0046 0.0089
Rh 0.4112 0.4072 0.0040 0.0097
Pooled 0.4653 0.4611 0.0043 0.0092
All (10) ABO 0.4794 0.4737 0.0057 0.0118
Rh 0.4103 0.4080 0.0023 0.0056
Pooled 0.4449 0.4409 0.0040 0.0090
Table 4. Gene diversity analysis for ABO and Rh loci in Saudi populations.
Al-Khobar Riyadh Jeddah South region Abha Tabuk/Madina Sakaka Domah Al-Qurayat
Al-Munawaara
Riyadh 0.0000
Jeddah 0.0002 0.0004
South region 0.0030 0.0034 0.0022
Abha 0.0029 0.0037 0.0019 0.0023
Tabuk/Madina Al-Munawaara 0.0007 0.0011 0.0004 0.0016 0.0008
Sakaka 0.0080 0.0075 0.0085 0.0069 0.0155 0.0103
Domah 0.0096 0.0087 0.0125 0.0191 0.0177 0.0123 0.0214
Al-Qurayat 0.0050 0.0045 0.0070 0.0097 0.0108 0.0064 0.0121 0.0021
Sweer 0.0091 0.0083 0.0119 0.0165 0.0166 0.0112 0.0184 0.0005 0.0009
Table 5. Genetic distance matrix showing the afnities between Saudi populations.
Dendrogram analyses
Based on the standard genetic distances matrix, dendrograms were constructed by
employing the unweighted pair-group method using arithmetic averages (UGPMA). An out-
lier with equal allele frequencies at both loci was added in the analyses. These analyses fur-
ther established the close afnities between the samples obtained from the populations of Al-
Khobar and Riyadh, between South and Tabuk/Madina Al-Munawaara, and between Domah
and Sweer (Figure 6). The sample of Jeddah joined the cluster of Al-Khobar and Riyadh,
Abha joined the cluster of South and Tabuk, and Al-Qurayat joined the cluster of Domah and
Sweer. Interestingly, among the northern four populations (i.e., Sakaka, Domah, Al-Qurayat,
and Sweer), Sakaka emerged distinct from the others. In contrast, Sakaka joined the clusters
of the middle and Southern populations.
Principal component analyses were performed to further elucidate the sample afni-
ties (Figure 7). These analyses iterated the clustering of the Northern populations and the
Eastern/Western samples. The distinct nature of Sakaka was also evident.

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Correlation between the allelic systems
In order to observe any potential association between the alleles, Spearman’s correla-
tions were calculated. The initial hypothesis was that there was no correlation(s) between the
alleles at one locus or alleles within the loci and all alleles existed independently. Alternatively,
there were correlations. Interestingly, signicant negative correlations were observed between
the p[A] and r[O] alleles, and between the q[B] and r[O] alleles at the ABO locus (Table 6).
The most remarkable correlation was observed between the q[B] and r[O] alleles (Pearson r2 =
Figure 7. Scatter plot exhibiting the results of principal component analyses.
Figure 6. Dendrogram based upon DA-UPGMA showing the genetic relationships between Saudi populations.
DA-UPGMA = alignment distance-unweighted pair-group method using arithmetic averages.

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-0.9160; 95%CI = -0.9803 to -0.6765; P = 0.0002; highly signicant). Furthermore, the p[A]
allele also showed association with the D (and d) allele at the Rh locus.
ABO locus Rh locus
p[A] q[B] r[O] D d
p[A] 1
q[B] 0.02 1
r[O] -0.42 -0.92 1
D 0.50 0.13 -0.32 1
d -0.50 -0.13 0.32 -1 1
Table 6. Correlation matrix between the allelic systems.
Clinal trends of phenotypic and allele frequencies
In order to observe any clinal trends for the studied parameters, the phenotypic and
allelic frequency data were mapped on the geography of Saudi Arabia (Figure 8). There were
remarkable geographic trends at blood types “B” and “O” and the q[B] and r[O] alleles. Blood
group “O” and the r[O] allele showed an increasing trend from North-East towards South-
West. Conversely, blood type “B” and the q[B] allele exhibited a decreasing trend from North-
East towards South-West (Figure 8).
Figure 8. Clinal analyses. The upper panel shows the clinal trends for allele q[B] and blood type “B”, while the
lower panel depicts the trends for allele r[O] and blood type “O”.

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DISCUSSION
The study of distribution of blood groups is useful for blood transfusion, organ trans-
plantation, genetic research, human evolution investigations, and forensic pathology. Blood
groups show associations between certain diseases and Rh and ABO incompatibilities of new-
borns (Klein and Anstee, 2005). Data for ABO and Rh loci in Saudi populations are limited.
This study attempted to draw a comprehensive picture of these polymorphisms in the Saudi
populations by analyzing various indices of gene diversity. Of the ten studied populations,
only the sample from Abha depicted deviations from HWE at the ABO locus. The inspection
of the phenotypic proportions showed that blood type “O” was overrepresented while type
“B” was strongly underrepresented in the Abha population. These variables resulted in an
increase in the frequency of the r[O] allele and a decrease in the frequency of the q[B] allele
(Tables 1 and 2). Deviations from HWE could result from non-random sampling and high
inbreeding. It is interesting to mention that Abha had the highest loss of heterozygosity at the
studied loci and a remarkable homozygosity was observed in this sample. The specic reasons
for this high homozygosity remain to be discovered. It is quite likely that there is wide-spread
consanguinity in this population. There are sporadic reports of high levels of consanguinity in
the Saudi populations but a country-wide pattern of inbreeding coefcients has not been eluci-
dated (el-Hazmi et al., 1995). Furthermore, compared to the Pakistani populations (which are
also highly inbred), heterozygosity appeared to be very low in the Saudi populations (Malik
and Amin-ud-Din, 2013; Ali and Malik, 2014; Rehman et al., 2014). It would be interesting to
investigate the relationship of consanguinity and the reduction of heterozygosity in the Saudi
as well as Pakistani populations (Hina and Malik, 2014; Jabeen and Malik, 2014).
The phenotypic and allelic frequencies of the populations of Al-Khobar, Riyadh, and
Jeddah were observed to be in close agreement with one another. It appeared that these popula-
tions of the Eastern, middle, and Western regions of Saudi Arabia had mixed populations due
to a cosmopolitan effect. They comprise the main urban assemblage of masses and therefore
contain people of mixed ethnicities. On the other hand, the populations in the North and South
are less admixed and more stratied. Interestingly, the stratication and sub-structuring in
the Saudi samples appear to be less remarkable than the estimates available for the Pakistani
populations of the Punjab Province (Shami and Rasmuson, 1994; Malik and Amin-ud-Din,
2013; Ali and Malik, 2014).
Homogeneity analyses allowed the identication of sub-clusters of Saudi populations
with similar characteristics. These population sub-clusters were further iterated by Nei’s mea-
sure of genetic distance and phylogenetic analyses. It is quite likely that the afnities exhibited
by the UPGMA tree are real. Alternatively, these similarities might have emerged due to close
geographic proximities of the studied populations, common evolutionary mechanisms, admix-
ture, or other stochastic factors. These analyses further revealed correlations between the allelic
systems q[B] and r[O]. There appeared to be a geographic trend operational at both alleles,
which was not obvious at allele p[A]. It could be anticipated that both of the aforementioned
alleles might have some selection pressure resulting in their characteristic distribution. It is
safe to conclude that the ABO locus is under certain evolutionary constraints. Different factors
like migrations, infectious diseases and immunological exposures, disease susceptibility, non-
random mating and inbreeding, and genetic drift are factors that confer evolutionary constraints
on human populations. It remains however unexplored which of these (or even other) factors
have shaped the current allelic landscape of the ABO and Rh genes in the Saudi population.

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E.S. AlSuhaibani et al.
©FUNPEC-RP www.funpecrp.com.br
Genetics and Molecular Research 14 (3): 7850-7863 (2015)
The ndings of this study need to be afrmed through highly polymorphic markers
such as microsatellites or by high-throughput methods. In a prospective study, it would be
pertinent to include a dense grid of samples from all major small and large populations, and
the samples should comprise both male and female individuals. It would be very interesting to
observe stratication in different Saudi populations and to estimate the loss of heterozygosity,
and to explore stratication at other loci. Furthermore, it would be worthwhile to check the
homozygosity existing in Saudi population at the genomic level, particularly in the context of
a high inbreeding coefcient.
The present study has some limitations. For example, there was a higher representa-
tion of male subjects in the data. Due to the traditional nature of Saudi society, the women
tended to stay at home, and hence, their data are under-represented. Furthermore, the blood
transfusion record could be biased towards more healthy males of a younger age while the data
of children and older subjects might be less represented. The positive aspect of this study is
the large sample size and the assemblage of large number of representative populations from
all geographic borders of Saudi Arabia.
This is the rst comprehensive study documenting the distribution of ABO and Rh
blood group types in ten cities of Saudi Arabia. It provided a country-wide picture of the
studied polymorphic markers and an initial glimpse into the allelic diversity of the studied loci.
Conicts of interest
The authors declare no conict of interest.
ACKNOWLEDGMENTS
The authors would like to extend their sincere appreciation to the DeanShip of
Scientic Research at King Saud University for funding this research group (#IRG14-05).
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