Genetic Diversity and Relationships among the Tribes of Meghalaya Compared to Other Indian and Continental Populations

The autosomal AmpFLSTR markers validated and widely used for forensic applications are used in this study to examine the extent of diversity and genetic relationships among nine Meghalaya populations. Altogether, 932 chromosomes from 9 populations were analyzed using 9 tetrameric AmpFLSTR loci. The included populations were all seven subtribes of the Austro-Asiatic Mon-Khmer-speaking Khasi and the neighboring Tibeto-Burman Garo. The Lyngngam, which are linguistically closer to the Khasi but are culturally intermediate between the Khasi and the Garo, are also included in the study. Although most of the microsatellite loci are highly polymorphic in each of these populations, the allele distributions are fairly uniform across the Meghalaya populations, suggesting relative homogeneity among them. Concurrent with this, the coefficient of gene differentiation (G(ST)) is observed to be low (0.026+/-0.002). This is naturally reflected in the lack of clear differentiation and clustering pattern of the Meghalaya tribes based on either geographic proximity or the historical or current affiliations of these tribes. Analysis of molecular variance (AMOVA) suggests no significant population structure. The structure analysis further suggests that, barring War-Khasi and Pnar, no other population shows any semblance of genetic identity. Even the position of the linguistically distinct Garo is not portrayed as separate from the Khasi. However, when comparable data from other Indian, Southeast Asian, and other continental populations were analyzed, the Meghalaya populations formed a compact cluster clearly separated from other populations, suggesting genetic identity of the Meghalaya populations as a whole. These results are concurrent with the hypothesis of a common and recent origin of these Meghalaya populations, whose genetic differentiation is overwhelmed by the homogenizing effect of continuous gene flow.

Mutation in the STR locus D21S1 1 of father causing allele mismatch in the child

We analyzed a case of paternity dispute with 15 autosomal STR loci and found a mismatch in one of the alleles of the locus D21S11 in the child. The composition of the alleles of this locus in the mother, suspicious father, and child were 29/32, 29/29, and 29/30, respectively. The combined paternity index (2.4 x 10(10)) and paternity probability (0.9999) suggest that the suspicious father is the biological father of the child. Further analysis of 6 Y chromosome STR loci revealed matching of all the Y chromosomal alleles of the child with that of the suspicious father. Since there was a perfect match of all the paternal alleles inherited (15 autosomal and 6 Y chromosomal) in the child with that of the suspicious father except the allele D21S11, it is suggested that this might be a case of mutation. Cloning and sequencing of all the alleles of the locus D21S11 of the suspicious father, mother, and the child helped in determining that the suspicious father contributed the mutated allele.

Phylogeography and Origin of Indian Domestic Goats

The Indian subcontinent contains 20 well-characterized goat breeds, which vary in their genetic potential for the production of milk, meat, and fibre; disease resistance; heat tolerance; and fecundity. Indian goats make up 20% of the world's goat population, but there has been no extensive study of these economically important animals. Therefore, we have undertaken the present investigation of 363 goats belonging to 10 different breeds from different geographic regions of India using mtDNA sequence data from the HVRI region. We find evidence for population structure and novel lineages in Indian goats and cannot reconcile the genetic diversity found within the major lineage with domestication starting 10,000 years ago from a single mtDNA ancestor. Thus, we propose a more complex origin for domestic goats.

Y chromosome deletions in azoospermic men in India

Genetic factors cause about 10% of male infertility. Azoospermia factors (AZFa, AZFb, AZFc) are considered to be the most important for spermatogenesis. We therefore made an attempt to evaluate the genetic cause of azoospermia, Y chromosome deletion in particular, in Indian men. We have analyzed a total of 570 men, including 340 azoospermic men and 230 normal control subjects. DNA samples were initially screened with 30 sequence-tagged site (STS) markers representing AZF regions (AZFa, AZFb, AZFc). Samples, with deletion in the above regions were mapped by STS walking. Further, the deletions were confirmed by Southern hybridization using the probes from both euchromatic and heterochromatic regions. Of the total 340 azoospermic men analyzed, 29 individuals (8.5%) showed Y chromosome deletion, of which deletion in AZFc region was the most common (82.8%) followed by AZFb (55.2%) and AZFa (24.1%). Microdeletions were observed in AZFa, whereas macrodeletions were observed in AZFb and AZFc regions. Deletion of heterochromatic and azoospermic regions was detected in 20.7% of the azoospermic men. In 7 azoospermic men, deletion was found in more than 8.0 Mb spanning AZFb and AZFc regions. Sequence analysis at the break points on the Y chromosome revealed the presence of L1, ERV, and other retroviral repeat elements. We also identified a approximately 240-kb region consisting of 125 bp tandem repeats predominantly comprised of ERV elements in the AZFb region. Histological study of the testicular tissue of the azoospermic men, who showed Y chromosome deletion, revealed complete absence of germ cells and presence of only Sertoli cells.

Sperm mitochondrial mutations as a cause of low sperm motility

We report the unique case of a 28-year-old man who, in spite of having a varicocele and a sperm concentration of 5 million/mL, of which 10% were motile and 20% had normal forms (oligoasthenoteratozoospermia [OAT]), was fertile. This was confirmed by paternity testing using 16 autosomal and 6 Y-chromosomal short tandem repeat (STR) loci. An analysis of mitochondrial genes that included cytochrome oxidase I (COI), cytochrome oxidase II (COII), adenosine triphosphate synthase6 (ATPase6), ATPase8, transfer ribonucleic acid (tRNA) serine I, tRNA lysine, and NADH dehydrogenase3 (ND3) revealed, for the first time, 9 missense and 27 silent mutations in the sperm's mitochondrial DNA (mtDNA) but not in the DNA from the blood cells. There was a 2-nucleotide deletion in the mitochondrial COII genes, introducing a stop codon, which might be responsible for low sperm motility.

Genetic affinities of the Andaman Islanders, a vanishing human population

BACKGROUND

The Andaman Islands in the Bay of Bengal are inhabited by hunter-gatherers of unknown origin, now on the verge of extinction. The Andamanese and other Asian small-statured peoples, traditionally known as "Negritos," resemble African pygmies. However, it is generally believed that they descend from the early Australo-Melanesian settlers of Southeast Asia and that their resemblance to some Africans is due to adaptation to a similar environment, rather than shared origins.

RESULTS

We analyzed mitochondrial DNA (mtDNA) sequences and RFLP polymorphisms, and Y chromosome biallelic markers and microsatellites, in present-day Andamanese of the Onge, Jarawa, and Great Andamanese tribes, and of inhabitants of the neighboring Nicobar Islands. We also analyzed mtDNA sequences from Andamanese hair samples collected by an ethnographer during 1906-1908. Living Andamanese exhibit low genetic variability that is consistent with their small population size and reproductive isolation.

CONCLUSIONS

Our data indicate that the Andamanese have closer affinities to Asian than to African populations and suggest that they are the descendants of the early Palaeolithic colonizers of Southeast Asia. In contrast, the Nicobarese have genetic affinities to groups widely distributed throughout Asia today, presumably descended from Neolithic agriculturalists.

CAG repeat expansion in the androgen receptor gene is not associated with male infertility in Indian populations

CAG repeat expansion in exon 1 of the androgen receptor (AR) gene has been reported to be associated with male infertility in some but not all populations. Until now, studies have not been carried out to examine this among Indian populations. For the first time, we have analyzed the CAG repeat motif in the AR gene in 280 men with azoospermia and in 201 men with normal fertility. The mean number of CAG repeats in the AR gene of men with azoospermia was 21.7 +/- 0.18, with a high incidence of repeat number 22. Among fertile-control men, the mean number of CAG repeats was 22.4 +/- 0.19, with a predominance of repeat number 23. The highest number of CAG repeats (32) was found with low frequency in both fertile and azoospermic groups. Comparison of fertile men and those with azoospermia on the basis of CAG repeats revealed that the number of CAG repeats in both groups were similar, as revealed with a paired t test (t = 0.04; P =.967). Expansion of the CAG repeat in the AR gene is therefore not associated with male infertility in Indian populations. This suggests that what is true for one population may not be true for other populations.

Is the amelogenin gene reliable for gender identification in forensic casework and prenatal diagnosis?

In humans, the amelogenin gene is present on both the X and the Y chromosomes. However, there are size differences in this gene between these chromosomes, which have been utilised for sexing in forensic casework and prenatal diagnosis. Our study using the AmpFl STR Profiler Plus kit, showed a deletion of Y chromosome-specific amelogenin in five Indian males (1.85%). We propose to call them "deleted-amelogenin males" (DAMs), who but for the detection of the presence of other Y-specific markers (e.g. SRY, STR and 50f2) would have been identified as females. Considering the consequences of the result obtained only using the amelogenin marker, we suggest the use of additional Y chromosome markers for unambiguous gender identification.

Y-chromosome and mitochondrial DNA polymorphisms in Indian populations

Y-chromosome polymorphism using short tandem repeat (STR) markers on 94 normal males belonging to the Brahmin and Kamma caste populations of Andhra Pradesh, India, and Siddis, a migrant population from Africa, inhabiting Hyderabad, India, revealed heterogeneity as indicated by network analysis. We have observed population-specific haplotypes and alleles. Analysis of Y-Alu polymorphism (YAP) in Siddis showed the presence of Alu insertion in 40% of the individuals. However, YAP insertion was not found in Brahmins and Kammas. The dendrogram based on hypervariable region I (HVR I) of the displacement loop (D-loop) sequence of mitochondrial DNA (mtDNA) of Siddis showed genetic relationships to African populations. YAP and mtDNA analysis of Siddis also confirmed their immigration from Africa.

Recurrent duplication and deletion polymorphisms on the long arm of the Y chromosome in normal males

Deletion of the 50f2/C (DYS7C) locus in interval 6 of Yq has previously been reported as a polymorphism in three males. We describe a survey of worldwide populations for further instances of this deletion. Of 859 males tested, 55 (approximately 6%) show absence of the 50f2/C locus; duplication of the locus was also detected in eight out of 595 males (approximately 1.4%). Populations having the deletion are confined to Asia, Australasia, and southern and northern Europe; of those of reasonable sample size, Finns had the highest deletion frequency (55%; n = 21). The deletions vary in size and the larger ones remove some of the RBM (RNA Binding Motif) genes, but none of the deletion males lack DAZ (Deleted in AZoospermia), a candidate gene for the azoospermia factor. On a tree of Y haplotypes, 28 deletion and eight duplication chromosomes fall into six and four haplotypic groups respectively, each of which is likely to represent an independent deletion or duplication event. Microsatellite and other haplotyping data suggest the existence of at least two further classes of deletion. Thus duplications and deletions in this region of Yq have occurred many times in human evolution, but remain useful markers for paternal lineages.

Efficient laser action from two cw laser-pumped pyrromethene-BF(2) complexes

Two new pyrromethene-BF(2) dyes, P-556 and P-567, are tested for cw laser operation. P-556 demonstrates a significant advance in the 530-620-nm region over commercially currently available dyes, where the best cw dyes in any range have peak efficiencies of the order of 35% and dyes in this range typically have less then 25%. The P-556 has a cw efficiency of 45% at the peak.

Laser dye spectroscopy of some pyrromethene-BF(2) complexes

To improve the laser action properties of the pyrromethene-BF(2) (P-BF(2)) complexes, we studied substitution effects at different positions of the dye molecule on the electronic spectra of several derivatives. Specifically, we used laser photoselection spectroscopy to measure the triplet-triplet (T-T) absorption and polarization spectra as well as the fluorescence and visible absorption singlet-singlet (S-S) spectra of the following compounds: 1,2,3,5,6,7,8-heptamethyl; 8-acetoxymethyl-1,3,5,7-tetramethyl-2,6-diethyl; 1,3,5,7-tetramethyl-8-p-methoxyphenyl; 3,5-dimethyl-1,7-diphenyl; and 1,3,5,7,8-pentamethyl- 2,6-diphenyl P-BF(2) complexes. The 1,3,5,7-tetramethyl P-BF(2) complex itself exhibits weak T-T absorption, which stretches from the green to the near-IR spectral region. This band consists of two overlapping (differently polarized) T-T transitions. Short molecular axis (i.e., 8 and 1,7 positions) substitution causes the positively polarized T-T transition to gain considerably in intensity. Significantly, the negatively, long-axis-polarized T-T transition was unaffected by the long-axis 2,6- position disubstitution. Therefore, only the 2,6-position disubstitution is expected to produce superior new P-BF(2) complex laser dyes. Substitution effects from strongly interacting groups with chromophores on S-S as well as T-T absorption spectra, together with cw laser photoselection spectroscopy, are briefly reviewed.

The genetic composition of an endogamous Adi-Dravidar population of Tamil Nadu

A total of 204 blood samples were collected from healthy, unrelated Adi-Dravidars of Chengalput District, Tamil, India. These samples were screened for ABO and RH blood groups using the respective antisera. CP and ALB serum protein electrophoretic phenotypes were assessed. The chi 2 analysis for Hardy-Weinberg equilibrium revealed that the population fits in panmictic equilibrium. The results were compared with the findings reported for other populations of Southern India.

Laser action from 2,6,8-trisubstituted-1,3,5,7-tetramethyl-pyrromethene-BF(2) complexes: part 2

In laser activity 1,3,5,7-tetramethyl-2,6-dicarboethoxy-8- cyanopyrromethene-BF(2)complex 5 under flash-lamp excitation was approximately 1.8 times more energy efficient than Rhodamine-B; about the same efficiency of Rhodamine-575 was found for 1,3,5, 7-tetramethyl-2,6,8-triethylpyrromethene- BF(2) complex 2.

Laser action from 2,6,8-position trisubstituted 1,3,5,7-tetramethylpyrromethene-BF(2) complexes: part 1

Of the four new pyrromethene derivatives studied, 1,3,5,7,8-pentamethyl-2,6-diethylpyrromethene-BF(2) complex lased ~3 times more efficiently than rhodamine 560 under flashlamp excitation.