Revision summary
Aberrations are numerical or structural changes of chromosomes. Down syndrome is trisomy 21 with body and cognitive effects. Turner is 45,X; Klinefelter is 47,XXY; both alter gonads and sometimes learning. Deletions and unbalanced translocations can be as severe as extra chromosomes. Outcomes vary; counselling and care matter as much as the karyotype name.
Model answer
Introduction
Chromosomal aberrations are changes in number or structure of chromosomes. They can alter development of body and brain because many genes move together.
Body
Numerical change
- Down syndrome (trisomy 21) produces distinctive facies, hypotonia, heart defects, and a range of intellectual disability. Maternal age raises risk of nondisjunction.
- Turner syndrome (45,X) affects females: short stature, ovarian dysgenesis, and sometimes spatial and social-cognitive difficulties. Intelligence is often near typical range, but the body is marked.
- Klinefelter syndrome (47,XXY) affects males: taller stature, hypogonadism, infertility, and a raised rate of language and learning problems.
- Other aneuploidies, such as trisomy 13 and 18, are often lethal early. Sex-chromosome aneuploidy is more survivable because of X inactivation.
Structural change
- Deletions, duplications, inversions, and translocations can be balanced in a parent and havoc in the child. Cri-du-chat (5p deletion) affects larynx and cognition.
- Reciprocal translocations explain some recurrent miscarriage and, if unbalanced, malformation syndromes.
Body and mind
- The phrase in the question is clinical: heart, gonad, stature, and language networks are all gene-rich. Havoc is variable, not a single fate.
- Counselling uses karyotype, now often microarray and NGS, plus pedigree. Anthropology adds stigma, schooling, and care, not a racial reading of the karyotype.
Flow diagram
flowchart TD CA[Chromosomal aberration] --> NUM[Aneuploidy] CA --> STR[Deletion translocation] NUM --> D[Down Turner Klinefelter] D --> BM[Body and mind phenotype]
Conclusion
Aneuploidy and rearrangements can disrupt growth, gonads, heart, and cognition. Down, Turner, and Klinefelter are the teaching examples. Severity is a spectrum, not a sentence.
Quick related
Students also ask
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Explain the significance of screening and counseling for genetic disorders.
Next question on this syllabus topic (2016 · Q7(b)). View answer →
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Are all chromosomal disorders equally severe?
No. Autosomal trisomies of large chromosomes are often lethal. Sex-chromosome aneuploidy is often milder.
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Can a balanced translocation be silent?
Yes in the carrier. Unbalanced gametes can then cause miscarriage or an affected child.
PYQ trend
When UPSC asked this
Related PYQs from other years, newest first. Open a question to read it.
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2024 · Q3(a) · Anthropology GS 1 · 20 marks
What is meant by karyotype? How does its analysis help in diagnosis of the chromosomal aberrations in man? -
2023 · Q8(b) · Anthropology GS 1 · 15 marks
Describe the causes of structural abnormalities of chromosomes with suitable examples. -
2016 · Q7(b) · Anthropology GS 1 · 15 marks
Explain the significance of screening and counseling for genetic disorders. -
2015 · Q6(c) · Anthropology GS 1 · 15 marks
Discuss chromosomal aberrations in man illustrating with examples
More from this topic
Q3(a) · UPSC Mains 2024 · Anthropology GS 1 · 20 marks
What is meant by karyotype? How does its analysis help in diagnosis of the chromosomal aberrations in man?
Numerical and structural aberrations (disorders).
Karyotype means chromosome complement; karyogram is its ordered image. Metaphase arrest, hypotonic spreading and G-banding permit homologous pairing and notation. It diagnoses trisomy 21, Turner, Klinefelter and other numerical aberrations. It also finds large deletions, inversions and balanced or unbalanced translocations. Multiple cells must be examined for mosaicism. A normal karyotype does not exclude microdeletions or single-gene disease; use FISH, microarray or sequencing appropriately.
Q8(b) · UPSC Mains 2023 · Anthropology GS 1 · 15 marks
Describe the causes of structural abnormalities of chromosomes with suitable examples.
Numerical and structural aberrations (disorders).
Structural abnormalities rearrange chromosome parts after breakage or unequal crossing-over. Types are deletion, duplication, inversion, translocation, ring, and isochromosome. Cri-du-chat is 5p deletion; 22q11 is a common microdeletion. Philadelphia t(9;22) is a somatic translocation in CML. Robertsonian 14;21 can cause translocation Down syndrome. Balanced parental carriers explain some recurrent unbalanced offspring.
Q7(b) · UPSC Mains 2016 · Anthropology GS 1 · 15 marks
Explain the significance of screening and counseling for genetic disorders.
Numerical and structural aberrations (disorders).
Screening searches a defined group for genetic risk. Newborn, cascade, and prenatal programmes are the main types. Counselling explains risk without directing the choice. Significance is prevention, early treatment, and informed reproduction. Stigma and eugenics are the failures to avoid.
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