Consanguinity, twinning and secondary sex ratio in the population of Karnataka, south India

The Impact of Lifestyle on the Secondary Sex Ratio: A Review

The secondary sex ratio (SSR), indicating the ratio of male to female live births, has garnered considerable attention within the realms of reproductive biology and public health. Numerous factors have been posited as potential trendsetters of the SSR. Given the extensive research on the impact of daily behaviors and habits on individuals' reproductive health, there is a plausible suggestion that lifestyle choices may also influence the SSR. By synthesizing the existing literature on the current research field, this comprehensive review indicates that an elevated SSR has been associated with an increased intake of fatty acids and monosaccharides, proper nutrition, higher educational levels, financial prosperity, and favorable housing conditions. On the other hand, a decreased SSR may be linked to undernutrition, socioeconomic disparities, and psychological distress, aligning with the Trivers-Willard hypothesis. Occupational factors, smoking habits, and cultural beliefs could also contribute to trends in the SSR. Our review underscores the significance of considering the aforementioned factors in studies examining the SSR and emphasizes the necessity for further research to unravel the mechanisms underpinning these connections. A more profound comprehension of SSR alterations due to lifestyle holds the potential to adequately develop public health interventions and healthcare strategies to enhance reproductive health and overall well-being.

Leukodystrophies and Genetic Leukoencephalopathies in Children Specified by Exome Sequencing in an Expanded Gene Panel

The overlapping clinical and neuroimaging phenotypes of leukodystrophies pose a diagnostic challenge to both clinicians and researchers alike. Studies on the application of exome sequencing in the diagnosis of leukodystrophies are emerging. We used targeted gene panel sequencing of 6440 genes to investigate the genetic etiology in a cohort of 50 children with neuroimaging diagnosis of leukodystrophy/genetic leukoencephalopathy of unknown etiology. These 50 patients without a definite biochemical or genetic diagnosis were derived from a cohort of 88 patients seen during a 2.5-year period (2015 January-2017 June). Patients who had diagnosis by biochemical or biopsy confirmation (n = 17) and patients with incomplete data or lack of follow-up (n = 21) were excluded. Exome sequencing identified variants in 30 (60%) patients, which included pathogenic or likely pathogenic variants in 28 and variants of unknown significance in 2. Among the patients with pathogenic or likely pathogenic variants, classic leukodystrophies constituted 13 (26%) and genetic leukoencephalopathies 15 (30%). The clinical and magnetic resonance imaging (MRI) findings and genetic features of the identified disorders are discussed.

Phenotyping and genotyping of skeletal dysplasias: Evolution of a center and a decade of experience in India

Genetic heterogeneity, high burden and the paucity of genetic testing for rare diseases challenge genomic healthcare for these disorders in India. Here we report our experience over the past decade, of establishing the genomic evaluation of skeletal dysplasia at a tertiary university hospital in India. Research or clinical genomic testing was carried out by Sanger sequencing and next-generation sequencing. Close national and international collaborations aided phenotyping and genotyping. We report 508 families (557 affected individuals) with the definitive molecular diagnosis of skeletal dysplasia. Dysostoses multiplex (n = 196), genetic inflammatory/rheumatoid-like osteoarthropathies (n = 114) and osteogenesis imperfecta and decreased bone density (n = 58) were the most common diagnoses. We enumerate the processes, clinical diagnoses and causal variants in the cohort with 48 novel variants in 21 genes. We summarize scientific contributions of the center to the description of clinical and mutation profiles and discovery of new phenotypes and genetic etiology. Our study illustrates the establishment and application of genomic testing tools for genetic disorders of skeleton in a large cohort. We believe this could be a model to emulate for other developing genetic centers.

Trends in consanguineous marriage in Karnataka, South India, 1980–89

Analysis of data on 106,848 marriages in the cities of Bangalore and Mysore, South India, between 1980 and 1989 showed that levels of consanguineous marriage varied between cities through time and by religion. The average coefficient of inbreeding was higher in Bangalore (F = 0·0339) than in Mysore (F = 0·0203), principally reflecting large-scale, post-Independence rural migration into Bangalore. Although there was some evidence of a decline in consanguineous marriages in Mysore, there was no convincing support in either city for earlier projections of a rapid reduction in the popularity of unions between close biological relatives.

Consanguinity affects selection of alpha-thalassemia genotypes and the size of populations under selection pressure from malaria

BACKGROUND

In populations with alpha(+)-thalassemia gene deletion, the practice of consanguineous marriages is common.

AIM

The study explored the impact of consanguinity (inbreeding) on the selection of alpha(+)-thalassemia genotypes in a computer model.

METHOD

In a population under selection pressure from malaria, a single protective mutation (-alpha/alphaalpha genotype) was introduced among normal genotypes (alphaalpha/alphaalpha), and mating allowed to proceed. Heterozygote (-alpha/alphaalpha) and homozygote (-alpha/-alpha) children were 1.5 and 2.5 times more likely to survive malaria than those with normal genotypes. Using different coefficients of inbreeding (F, range 0-0.12), we examined the effect of population size, and the mean number of generations required for the homozygote frequency to reach 0.5.

RESULTS

On average, consanguineous populations were larger than randomly mating populations and the size was directly proportional to F. In more inbred populations,-alpha/-alpha homozygotes reached a frequency of 0.5 faster than in less inbred populations. As the frequency of the alpha(+)-thalassemia allele in a population increases, however, the positive effect of inbreeding on the population growth decreases.

CONCLUSION

Under selection pressure from malaria, consanguinity may increase the speed of selection of-alpha/-alpha homozygotes and provide an advantage regarding population growth over non-consanguineous populations.

Consanguinity and its relevance to clinical genetics

Marriage between close biological relatives is generally regarded with suspicion and distaste within Western society, reflecting historical and religious prejudice. By comparison, in many other populations there is a strong preference for consanguineous unions, most frequently contracted between first cousins, and marriage outside the family is perceived as a risky and disruptive option. The increasing importance of the genetic contribution to the overall disease profile in both developed and developing countries has highlighted potential problems associated with detrimental recessive gene expression in consanguineous progeny. This review examines the outcomes of consanguineous unions, with proposals as to how the ongoing preference for consanguinity in many communities can best be accommodated from a clinical genetics perspective.

Consanguinity and reproductive behaviour in a tribal population 'the Baiga' in Madhya Pradesh, India

We have studied the marriage pattern and reproductive behaviour in a single Central Indian primitive tribe, the Baiga. Parents were consanguineous in 34% of marriages (19.2% mother's brother's daughter (MBD), 13.1% father's sister's daughter (FSD) and 1.7% were double first cross-cousins (DFCC). Fertility levels were significantly higher (p < 0.05) in related couples (4.7 offspring/couple) than unrelated couples (4.2/couple). Mortality (up to 20 years) was 19%. In the offspring of consanguineous couples it was higher (19.7%) than in the offspring of unrelated couples (18.6%) but the difference was not statistically significant. In consanguineous couples the reproductive period was longer than in unrelated couples, probably to allow compensation for increased reproductive losses (infant and childhood deaths). The level of social as compared to genetic parenting was about 35% as measured by tracking the inheritance of sickle gene, and allowance must be made for this in assessing the influence of consanguineous marriage on fertility and mortality.

Reproductive behavior and health in consanguineous marriages

In many regions of Asia and Africa, consanguineous marriages currently account for approximately 20 to 50% of all unions, and preliminary observations indicate that migrants from these areas continue to contract marriages with close relatives when resident in North America and Western Europe. Consanguinity is associated with increased gross fertility, due at least in part to younger maternal age at first livebirth. Morbidity and mortality also may be elevated, resulting in comparable numbers of surviving offspring in consanguineous and nonconsanguineous families. With advances in medicine and public health, genetic disorders will account for an increased proportion of disease worldwide. Predictably, this burden will fall more heavily on countries and communities in which consanguinity is strongly favored, as the result of the expression of deleterious recessive genes. However, studies conducted in such populations indicate that the adverse effects associated with inbreeding are experienced by a minority of families.

Epidemiology of diabetes in Asians of the Indian subcontinent

Asians from the Indian subcontinent have received greater attention in diabetes studies because of their migration in large numbers. The prevalence of non-insulin-dependent diabetes mellitus (NIDDM) in migrant Indians is higher than that in the population residing in the Indian subcontinent and is also usually higher than in the other racial groups in the host country. However, before drawing any conclusions with reference to the high prevalence of NIDDM in the migrant Indians, careful comparisons are required with more up-to-date information available from the Indian subcontinent itself. Recent data from India indeed indicate that the prevalence rates have either been underestimated in the past or are rising. The problem is compounded by the different diagnostic criteria used for defining diabetes. Some of the possible factors which cause variations in the rates of NIDDM in this population are discussed.

Consanguinity, spousal age at marriage and fertility in seven Pakistani Punjab cities

A retrospective study was conducted on spousal age at marriage, time to first birth and total pregnancies in the populations of seven cities in the Pakistani province of Punjab. Consanguineous marriages were strongly favoured with coefficients of inbreeding (F) for the present generation ranging from 0.0236 to 0.0286. Male and female ages at marriage were younger in consanguineous unions and spousal age differences smaller than in their non-consanguineous counterparts. Time elapsed from marriage to first birth tended to be longer in consanguineous unions but, in general, they had more pregnancies. As consanguinity has been shown to be associated with increased ante- and postnatal mortality in these communities, reproductive compensation provides a credible explanation for the apparent enhanced fertility with inbreeding. However, the data equally could be interpreted in terms of greater reproductive span and/or biosocial compatibility of the consanguineous unions.