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Home/Anthropology/Mains PYQ/2024/Paper I/Human Genetics & Human Biology
UPSC MainsAnthropology Optional Paper I 2024 20 Marks Model Answer Available

Karyotype and Diagnosis of Chromosomal Aberrations — 2024 Paper I

Question · 2024 · Paper I · 20 Marks

What is meant by karyotype? How does its analysis help in diagnosis of the chromosomal aberrations in man?

Model Answer

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Introduction

A karyotype is the complete chromosome complement of an individual, described according to chromosome number, size, shape, centromere position and banding pattern. Its arranged photographic representation is called a karyogram. A normal human somatic cell has 46 chromosomes, written as 46,XX in females and 46,XY in males. Tjio and Levan (1956) established the correct human chromosome number as 46.

Preparation of Karyotype

Dividing cells are obtained from blood, bone marrow, skin, amniotic fluid or chorionic villi. They are cultured and arrested at metaphase using colchicine. After hypotonic treatment, fixation and staining—commonly G-banding—the chromosomes are paired according to size, centromere position and banding pattern.

Diagnosis of Chromosomal Aberrations

Numerical abnormalities

Karyotyping identifies extra or missing chromosomes:

  • Trisomy 21—Down syndrome
  • Trisomy 18—Edwards syndrome
  • Trisomy 13—Patau syndrome
  • 45,X—Turner syndrome
  • 47,XXY—Klinefelter syndrome
  • Triploidy and other polyploid conditions

Structural abnormalities

Changes in chromosome length and banding pattern reveal:

  • deletions, such as 5p deletion in Cri-du-chat syndrome;
  • duplications;
  • inversions;
  • reciprocal and Robertsonian translocations;
  • ring chromosomes and isochromosomes.

It also distinguishes free trisomy 21 from translocation Down syndrome, which is important for estimating recurrence risk.

Other applications

  • Detection of mosaicism, such as 45,X/46,XX
  • Prenatal diagnosis through amniocentesis or chorionic-villus sampling
  • Investigation of infertility and repeated miscarriages
  • Detection of acquired abnormalities in cancers, such as the Philadelphia chromosome in chronic myeloid leukaemia

Treatment and Management

Most constitutional chromosomal abnormalities cannot be completely corrected. Management is therefore condition-specific and may include:

  • early developmental and educational support;
  • treatment of heart, hearing, vision or endocrine problems;
  • physiotherapy and occupational therapy;
  • hormone therapy in Turner or Klinefelter syndrome;
  • surgery for associated congenital defects;
  • fertility support and genetic counselling;
  • specific anti-cancer treatment for acquired chromosomal abnormalities.

Thus, early diagnosis improves planning, treatment and quality of life even when the basic chromosomal defect remains unchanged.

Anthropological and Applied Perspective

Karyotype studies contribute to population cytogenetics by examining chromosomal variation, reproductive loss and genetic disorders among different populations. Medical anthropology further emphasises:

  • culturally sensitive genetic counselling;
  • awareness regarding the effects of close-kin marriage and prolonged endogamy without stigmatising communities;
  • community-based screening where recurrent congenital disorders or miscarriages are reported;
  • informed consent, confidentiality and reproductive autonomy;
  • social inclusion and reduction of stigma towards affected individuals.

Limitations

Conventional karyotyping detects mainly large chromosomal changes and cannot identify point mutations or many microdeletions. Therefore, it is supplemented by FISH, chromosomal microarray and DNA sequencing.

Conclusion

Karyotype analysis provides a genome-wide picture of chromosome number and structure. Besides diagnosing congenital, reproductive and cancer-related abnormalities, its anthropological application lies in understanding population variation and developing culturally appropriate genetic counselling and community-health interventions.

2026 How would you find out that a particular disease/disorder is inherited and, if so, in which manner? Elaborate with suitable examples. 2026 What do you understand by fertility and mortality? How are these influenced by biological and socio-ecological factors? 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?

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UPSC Anthropology Optional 2024 — Paper I

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10 Marks150 words
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10 Marks150 words
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