Write notes on the following in about 150 words each: (a) Balanced and transient genetic polymorphism. (10 marks) (b) Genetic…

(a) Balanced and Transient Genetic Polymorphism

Genetic polymorphism refers to the simultaneous occurrence of two or more discontinuous genetic variants (alleles) in a population, where the rarest morph frequency exceeds 1%, ruling out mutation pressure alone (E.B. Ford).

Balanced Polymorphism: A stable equilibrium where natural selection actively maintains multiple alleles over generations at frequencies higher than expected by mutation. It typically operates via heterozygote advantage (overdominance), frequency-dependent selection, or environmental heterogeneity. The classic human example is the sickle-cell trait (HbA/HbS). In malaria-endemic zones like tropical Africa and tribal pockets of Central India (e.g., Gond, Bhil), heterozygous individuals possess selective resistance against Plasmodium falciparum, balancing the lethal effects of homozygous sickle-cell anemia (HbS/HbS) and normal susceptibility (HbA/HbA).

Transient Polymorphism: A temporary, dynamic phase during which one allele progressively replaces another under directional selection until the favored allele reaches fixation. It reflects an evolving population adapting to a directional ecological shift. The standard paradigm is industrial melanism in the peppered moth (Biston betularia), where the melanic morph temporarily outcompeted the light morph due to soot-covered trees, only to reverse when pollution abated. In humans, transient polymorphisms occur during the rapid geographic spread of novel adaptive alleles, such as lactase persistence or specific drug-resistant pathogen strains.

(b) Genetic Imprinting in Human Diseases

Genetic imprinting is a non-Mendelian epigenetic phenomenon wherein gene expression is regulated in a parent-of-origin specific manner. Through DNA methylation and histone modifications during gametogenesis, one parental allele is selectively silenced (imprinted), while only the allele inherited from the other parent remains transcriptionally active.

Disruption of this monoallelic expression—through microdeletions, loss of imprinting, epimutations, or Uniparental Disomy (UPD, where an individual inherits both chromosome copies from a single parent)—causes severe developmental and metabolic syndromes:

Prader-Willi Syndrome (PWS): Results from the loss of expression of paternally active genes in the 15q11-q13 chromosomal region, caused by paternal microdeletion (~70%), maternal uniparental disomy (UPD15, ~25%), or imprinting center defects. Phenotypically manifests as neonatal hypotonia, infantile failure to thrive, followed by hyperphagia, morbid obesity, and hypogonadism.

Angelman Syndrome (AS): Arises from the loss of maternal expression of the UBE3A gene within the same 15q11-q13 region, via maternal deletion (~70%), paternal UPD15 (~7%), or UBE3A mutations. It is characterized by severe intellectual disability, ataxic gait, absent speech, and unprovoked paroxysms of laughter.

Beckwith-Wiedemann Syndrome (BWS): Involves dysregulation of imprinted growth-regulatory genes on chromosome 11p15.5 (such as IGF2 and CDKN1C), causing somatic overgrowth, macroglossia, and pediatric embryonal tumors.

Imprinting highlights how epigenetic errors can drive pathogenesis without structural alterations in the primary DNA sequence.

(c) Stages of Human Pre-natal Development

Human prenatal development spans approximately 38 to 40 weeks (gestational age) from fertilization to parturition, divided auxologically into three distinct sequential phases:

1. Germinal Stage (0 to 2 weeks): Initiated at fertilization in the fallopian tube, forming a single-celled diploid zygote. It undergoes rapid mitotic cleavage to form a morula, which subsequently develops into a fluid-filled blastocyst comprising an inner cell mass (embryoblast) and an outer layer (trophoblast). The phase concludes with the complete implantation of the blastocyst into the maternal endometrium by day 10–14.

2. Embryonic Stage (3 to 8 weeks): Characterized by rapid cellular differentiation, gastrulation into three primary germ layers (ectoderm, mesoderm, endoderm), and organogenesis. Key milestones include neural tube formation and closure, primitive heart pulsation (by week 4), and limb bud emergence. This stage represents the critical window of development; tissues are exceptionally vulnerable to environmental teratogens (e.g., thalidomide, rubella, alcohol), which cause major structural congenital malformations.

3. Fetal Stage (9 weeks to Birth): Dominated by somatic growth, histogenesis, and functional maturation of organ systems. Bone ossification accelerates, sexual differentiation is morphologically distinct by week 12, and neuromuscular activity increases (quickening). The threshold of fetal viability is achieved around 24 weeks with pulmonary surfactant synthesis, leading up to term birth where adipose accumulation and neuro-development prepare the neonate for extrauterine survival.

(d) Shaman, Sorcerer and Medicine Man

Anthropological study of magico-religious specialists classifies practitioners based on their recruitment, social legitimacy, techniques, and structural functions within traditional societies.

Shaman: An ecstatic, part-time religious specialist who derives power through direct, personal spiritual selection (often preceded by an initiatory illness or crisis). The shaman operates on behalf of the community via Altered States of Consciousness (ASC), trance, and "soul flight" to negotiate with the spirit world, divine events, and heal illnesses (e.g., Siberian Tungus, or the *Ojha*/*Sokha* among the Santhal and Munda). Shamanic practice holds high institutional legitimacy and serves public, integrative functions.

Sorcerer: A practitioner of malevolent magic who uses learned, mechanical rites, spells, and physical paraphernalia (e.g., poisons, nail pairings, sympathetic effigies) to inflict harm, disease, or misfortune. Sorcery relies on acquired techniques rather than innate spiritual possession. Unlike the shaman, the sorcerer operates covertly and anti-socially; sorcery accusations (e.g., Azande ngua, or Dakin accusations in tribal India) function as mechanisms of social tension management and moral control.

Medicine Man: An empirical-rational healer whose role is rooted in ethnomedical knowledge, herbal pharmacology, bone-setting, and diagnostic techniques (e.g., traditional Vaidya, Kaviraj, or indigenous root doctors). While their practice may incorporate ritual purification and incantations, their primary efficacy is naturalistic rather than purely spiritual. They occupy a recognized, legitimate, and secular therapeutic office focused on somatic restoration.

(e) Household and Domestic Group

While often used interchangeably in popular discourse, anthropology distinguishes between the household and the domestic group based on spatial, structural, and developmental criteria.

Household: A residential and commensal unit whose members share a common physical dwelling, pool economic resources, and consume food prepared from a common hearth ("chulah"). The United Nations defines a household primarily on co-residence and shared socio-economic arrangements. It is a spatial and demographic construct, which can be nuclear, sub-nuclear, or extended, and may include unrelated individuals (e.g., domestic servants or lodgers).

Domestic Group: A broader, task-oriented kinship unit organized around biological reproduction, primary socialization, economic cooperation, and intergenerational transmission of property and status. Members of a domestic group may not always co-reside within the same physical household. For example, in migrant labor contexts in rural India, family members residing in urban centers remain functionally, economically, and ritually integrated into the village domestic group through regular remittances and ritual participation.

Analytical Significance: Meyer Fortes and Jack Goody formulated the concept of the Developmental Cycle in Domestic Groups, showing that domestic units expand, disperse, and replace themselves over time. In Indian anthropology, A.M. Shah demonstrated that while the co-residential joint household may experience residential fission into nuclear households due to modern socioeconomic pressures, the broader joint domestic group persists through enduring mutual kinship obligations, property co-ownership, and ancestral rituals.