Critically discuss the Mendelian principles and their application to human

Model answer

Introduction

Mendel’s principles explain how discrete traits move from parents to offspring. In human populations they work, and they need Hardy–Weinberg, linkage, and culture before they become demography.

Body

The principles

Segregation: alleles of a locus separate in gametes. Independent assortment: unlinked loci mix independently.
Dominance is a phenotypic relation, not a moral one. Recessive traits hide in heterozygotes.
Mendel used peas. Humans added sex linkage, as in haemophilia, and mitochondrial exceptions.

Application to human populations

Pedigrees for albinism, PTC, achondroplasia, and thalassaemia are Mendelian teaching files.
Hardy–Weinberg turns Mendel into population frequencies if mating is random and selection is nil.
Consanguinity, studied by Sanghvi in India, raises homozygosity for recessives.
Blood groups applied Mendelism at scale. Forensic STRs still assume Mendelian transmission.

Critical limits

Most stature and skin traits are polygenic, not one-pea genes.
Linkage, imprinting, penetrance, and phenocopies break textbook ratios.
Culture decides who mates. Caste and village endogamy are not bean-bag random mating.
Eugenic misuse of Mendelism was political. Counselling today is voluntary and case-based.

Flow diagram

flowchart TD
  MEN[Mendel segregation assortment] --> PED[Human pedigrees]
  PED --> HW[Hardy Weinberg]
  HW --> LIM[Polygenic consanguinity culture]

Conclusion

Mendelian principles still govern single-locus human traits and forensic markers. Population application needs Hardy–Weinberg plus a map of marriage. Polygenic and cultural facts stop a pea-garden view of whole peoples.

Students also ask

Do all human traits Mendelise?

Single-locus diseases often do. Height and behaviour usually do not.

Is independent assortment always true?

No. Linked genes on one chromosome travel together until recombination.

Differentiate between pedigree and genealogical analyses. Discuss the history and application of these methods in anthropological studies

Human Genetics

Genealogy is Rivers’ 1910 method: social ties, kin terms, marriage and rights. Fictive kin count. Pedigree is a genetic diagram of biological parentage and affected status, used to infer Mendelian inheritance. The two words are not synonyms. History runs from Cambridge field kinship on one side to clinical and then medical genetics on the other. Uses include kinship systems, consanguinity, counselling, and careful overlay with consent. Alliance theory criticised genealogy-as-enough. It did not erase the method.

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Q3(c) · UPSC Mains 2023 · Anthropology GS 1 · 15 marks

What is mixed-longitudinal method of studying human growth. Discuss its merits and demerits.

Human Genetics

Cross-sectional study measures different children once. Longitudinal study remeasures the same children, as in Tanner’s work. Mixed-longitudinal study follows overlapping cohorts and may replace drop-outs. Merits are cost, speed, and some velocity data. Demerits are joining error, secular-trend mix, and remaining attrition bias. Indian school and ICMR work often uses this middle design.