Q.43 Give below are two statements : One is labelled as Assertion A and the other is labelled as Reason R
Assertion A : Klinefelter’s syndrome have minor phenotypic anomalies with small testis and enlarged breasts.
These individuals have 47 chromosomes with 44 autosomes plus XXY.
Reason R : Males with XYY syndrome have two Y chromosomes. Such individuals have anti social behavior
and aggression. Their frequency is approximately I to 650.
In the light of the above statements. choose the most appropriate answer from the options given below :
1. Both A and R are correct and R is the conect explanation ofA
2. Both A and R are correct but R is NOT the correct explanation of A
3. A is correct but R is not correct
4. A is not correct but R is correct.
Correct Answer: 2. Both A and R are correct but R is NOT the correct explanation of A
Klinefelter’s syndrome (47,XXY) features small testes and gynecomastia as key traits, while XYY syndrome involves an extra Y chromosome with a low incidence around 1:1000 males, though aggression links are overstated.
Assertion (A) Analysis
Assertion A correctly describes Klinefelter’s: minor anomalies like small testes (<4ml, hypospadias risk) and enlarged breasts (gynecomastia in ~80%). Karyotype is 47 chromosomes—44 autosomes + XXY—due to nondisjunction. Tall stature, infertility, low testosterone confirm this classic sex chromosome aneuploidy.
Reason (R) Analysis
Reason R accurately notes XYY (Jacob’s syndrome) has two Y chromosomes, frequency ~1:650-1000 males. However, “anti-social behavior and aggression” is a myth from early studies; most XYY men are normal height, fertile, without criminality—taller stature and minor learning issues predominate.
Option Breakdown
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Option 1: Both correct, R explains A—False. R describes unrelated syndrome.
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Option 2: Both correct, R not explanation—True. Independent facts on distinct disorders.
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Option 3: A correct, R incorrect—False. R’s karyotype/frequency right, behavior outdated.
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Option 4: A incorrect, R correct—False. A matches diagnostics precisely.
Klinefelter Syndrome XXY and XYY: Assertion Reason Genetics Guide
Klinefelter syndrome XXY and XYY syndromes are sex chromosome disorders tested in exams, with Klinefelter syndrome XXY showing small testis, enlarged breasts, and 47 chromosomes, distinct from XYY’s extra Y traits.
Klinefelter Syndrome (47,XXY) Features
Affects 1:500-1000 males from meiotic nondisjunction. Extra X disrupts testicular development:
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Hypogonadism: small testes, azoospermia, low testosterone.
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Gynecomastia, tall stature, gynecomastia, weaker muscles.
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Diagnosis: karyotype shows 44A + XXY; treat with testosterone.
XYY Syndrome Characteristics
“Super male” fallacy debunked: 1:650-1000 births, often asymptomatic.
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Tall (>6ft), normal fertility.
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No proven aggression link; slight IQ/motor delays possible.
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Detected via amniocentesis; no routine intervention.
| Syndrome | Karyotype | Key Traits | Frequency |
|---|---|---|---|
| Klinefelter | 47,XXY | Small testes, gynecomastia, infertility | 1:500-1000 males |
| XYY | 47,XYY | Tall stature, normal fertility | 1:650-1000 males |
Assertion-Reason Exam Strategy
Both statements factual but unrelated—R doesn’t justify A’s XXY pathology. Common trap: confusing syndromes.
