1. (A)–(III); (B)–(II); (C)–(I); (D)–(IV)
2. (A)–(III); (B)–(I); (C)–(II); (D)–(IV)
3. (A)–(I); (B)–(IV); (C)–(II); (D)–(III)
4. (A)–(IV); (B)–(I); (C)–(III); (D)–(II)
Down syndrome results from trisomy 21, Klinefelter’s syndrome from an extra X chromosome, Turner’s syndrome from X chromosome loss, and Cri du chat from a chromosome 5 deletion. The correct matching is option 2.
Correct Answer
Option 2: (A)–(III); (B)–(I); (C)–(II); (D)–(IV)
This pairs:
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(A) Down syndrome with (III) Trisomy of chromosome 21.
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(B) Klinefelter’s syndrome with (I) Gain of X-chromosome.
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(C) Turner’s syndrome with (II) Loss of X-chromosome.
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(D) Cri du chat syndrome with (IV) Deletion of small terminal portion of chromosome 5.
Genetic Disorders Explained
Down Syndrome (Trisomy 21)
Typically 47 chromosomes with three copies of chromosome 21 (47, XX/XY + 21), causing intellectual disability, distinct facial features, and heart defects. 95% of cases arise from nondisjunction in meiosis.
Klinefelter’s Syndrome (Gain of X)
Males with 47, XXY karyotype due to extra X chromosome, leading to tall stature, hypogonadism, and infertility. Nondisjunction in parental gametes causes this sex chromosome gain.
Turner’s Syndrome (Loss of X)
Females with 45, X karyotype (monosomy X), resulting in short stature, webbed neck, and ovarian dysgenesis. Often from paternal X loss during meiosis.
Cri du Chat Syndrome (Chromosome 5 Deletion)
Deletion at 5p terminal region (46, XX/XY, 5p-), causing cat-like cry, microcephaly, and developmental delays. Arises from unbalanced translocation or breakage.
Options Analysis
| Option |
A (Down) |
B (Klinefelter) |
C (Turner) |
D (Cri du Chat) |
Correct? |
| 1 |
III |
II |
I |
IV |
No |
| 2 |
III |
I |
II |
IV |
Yes |
| 3 |
I |
IV |
II |
III |
No |
| 4 |
IV |
I |
III |
II |
No |
Option 1 swaps Klinefelter/Turner. Option 3 mismatches Down/Cri du chat. Option 4 confuses Down/Turner. Only 2 aligns all precisely.
NEET Exam Tips
Focus on karyotypes: Down (47+21), Klinefelter (47,XXY), Turner (45,X), Cri du chat (5p-). Practice matching questions for quick recall in genetics section.
