VAID'S ICS – Best UPSC Anthropology Coaching in Delhi Since 1985

Comprehensive Classroom Course · Admissions openRegister now
+91 93113 37737
  • +91-93113 37737, +91-99999 46748
  • 73(FF), Old Rajender Nagar Market, Delhi - 110060
  • MON to SUN 9.00 am - 6.00 pm
Facebook Youtube Instagram
Menu
Enquire Now
Home/Anthropology/Mains PYQ/2026/Paper I/Human Genetics & Human Biology
UPSC MainsAnthropology Optional Paper I 2026 20 Marks Model Answer Available

Determining the Inheritance of a Disease or Disorder — 2026 Paper I

Question · 2026 · Paper I · 20 Marks

How would you find out that a particular disease/disorder is inherited and, if so, in which manner? Elaborate with suitable examples.

Model Answer

VAID ICS
Approach

  • Demand of Question: Explain how to establish whether a disorder has a genetic basis and then identify its mode of inheritance.
  • Structuring the Response: Phenotype/family aggregation → three-generation pedigree → inheritance signatures → twin/population evidence → laboratory confirmation → exceptions/counselling.
  • Key Dimensions to Cover: Familial vs genetic vs inherited, AD/AR/X-linked/mitochondrial patterns, penetrance, de novo mutation, molecular/cytogenetic tests, counselling.

 

Model Answer

Introduction: A disorder cannot be called inherited merely because several relatives are affected; relatives also share diet, infections and social environments. The task is therefore two-stage: first establish a genetic contribution, and then infer the mode of transmission, followed by biological confirmation.

  1. Define the phenotype and test family aggregation:

Record diagnostic criteria, age at onset and severity. Obtain a detailed three-generation family history including affected/unaffected persons, miscarriages, consanguinity and ancestry. Compare recurrence among biological relatives with background population frequency and exclude obvious shared exposures or phenocopies.

  1. Pedigree analysis:

Construct a pedigree and examine vertical/horizontal transmission, sex ratio and parent–offspring patterns.

  • Autosomal dominant: usually vertical transmission; both sexes affected; father-to-son transmission possible. Example: Huntington disease.
  • Autosomal recessive: affected siblings may be born to unaffected carrier parents; may skip generations; consanguinity can increase occurrence. Examples: sickle-cell disease, cystic fibrosis.
  • X-linked recessive: mainly males affected; no father-to-son transmission; carrier mothers may transmit to sons. Examples: haemophilia A, Duchenne muscular dystrophy.
  • X-linked dominant: affected fathers transmit to all daughters and no sons; affected mothers may transmit to either sex.
  • Mitochondrial: affected mothers may transmit the mutation to children; affected fathers do not transmit mtDNA. Expression may vary because of heteroplasmy.
  1. Corroborative evidence:

Higher concordance in monozygotic than dizygotic twins supports a genetic component for complex traits, though shared environment must still be considered. Segregation/linkage and population studies may provide additional evidence.

  1. Biological confirmation:
  • Karyotyping or chromosomal microarray detects numerical/structural chromosome abnormalities.
  • Targeted variant analysis, gene panels and exome/genome sequencing can identify pathogenic variants and test co-segregation.
  • Biochemical tests may reveal abnormal proteins, enzymes or haemoglobin fractions.
  1. Interpret exceptions:

Reduced penetrance can make dominant traits appear to skip generations; variable expressivity changes severity; de novo mutations may produce an isolated affected child. Common disorders such as type 2 diabetes and hypertension are usually polygenic/multifactorial and should not be forced into simple Mendelian ratios.

Family history → pedigree → genetic hypothesis → laboratory test → segregation confirmation → counselling

Conclusion: The strongest inference comes when a characteristic pedigree pattern and molecular/cytogenetic evidence converge. This permits accurate recurrence-risk assessment and ethically informed genetic counselling.

2026 In what manner is our understanding of serogenetics and cytogenetics useful in reproductive biology? What are the major ethical issues involved in reproductive technology? 2026 Why the classifications of Indian populations, based on somatometric and somatoscopic characteristics failed to develop a common understanding of the population diversity? 2026 Canalization and catch-up growth. 2026 Genetic polymorphism and natural selection.

Want feedback on your answer?

Join the Anthropology workshop or get structured answer-writing guidance from VAID ICS.

Join Workshop Contact VAID ICS

UPSC Anthropology Optional 2026 — Paper I

28 questions

5(d) Anthropometry in ergonomics.

10 Marks150 words
Syllabus: Paper I > Applications of Anthropology > Ergonomics > Anthropometry
2026Paper IApplied & Forensic AnthropologyModel answer available

1(b) Canalization and catch-up growth.

10 Marks150 words
Syllabus: Paper I > Human Growth and Development > Growth patterns > Canalization and catch-up growth
2026Paper IHuman Genetics & Human BiologyModel answer available

5(c) Feminist movement and family.

10 Marks150 words
Syllabus: Paper I > Family > Contemporary trends > Feminist movement and family
2026Paper IMarriage & FamilyModel answer available

1(a) Health as a cultural construct.

10 Marks150 words
Syllabus: Paper I > Applications of Anthropology > Medical Anthropology > Culture and health
2026Paper IApplied & Forensic AnthropologyModel answer available

1(c) Myth as oral literature.

10 Marks150 words
Syllabus: Paper I > Religion, Myth and Ritual > Myth > Myth as oral literature
2026Paper IAnthropology of ReligionModel answer available

5(e) Thermoluminescence dating method.

10 Marks150 words
Syllabus: Paper I > Archaeological Anthropology > Dating methods > Thermoluminescence
2026Paper IPrehistoric ArchaeologyModel answer available