What is the NEET 2026 chromosomal disorders assertion-reason question?
Both statements are incorrect. The correct option is B.
Statement I links Down's syndrome to the absence of one X chromosome. Statement II links Turner's syndrome to an additional copy of a chromosome. The four options are:
This question tests the exact swap between autosomal trisomy and sex-chromosome monosomy. Students who mix the two syndromes select the wrong combination under negative marking.
What is the official step-by-step solution to the NEET 2026 chromosomal disorders assertion-reason question?
Down's syndrome is caused by trisomy of chromosome 21, which produces the karyotype . Absence of one X chromosome produces Turner's syndrome with karyotype .
Statement I is therefore incorrect because it attributes Down's syndrome to the absence of one X chromosome. Statement II is incorrect because Turner's syndrome results from a missing chromosome, not an additional copy.
The official method evaluates each statement independently against its verified karyotype, then matches the pattern of both incorrect to option B.
What is the common method mistake in chromosomal disorders assertion-reason questions?
Treating all chromosomal absence statements as interchangeable regardless of whether the chromosome is an autosome or sex chromosome produces the error. Students assign the absence of an X chromosome to Down's syndrome in Statement I without verification.
They fail to cross-check the exact karyotype ( versus ) before judging each statement independently. This leads to marking Statement I as correct and selecting option C or D.
Write the specific chromosome and total count beside each syndrome name the moment it appears. This single notation blocks the swap.
What key distinctions separate Down's, Turner's and Klinefelter syndromes in assertion-reason questions?
Down's syndrome is trisomy 21 with a total of 47 chromosomes. Turner's syndrome is monosomy X with karyotype 45 XO. Klinefelter syndrome is 47 XXY from an extra X chromosome.
Autosomal aneuploidy alters chromosomes 1-22 and affects both sexes equally. Sex-chromosome aneuploidy alters only the X or Y count and produces sex-specific karyotypes. Match the named syndrome to its exact total and chromosome type before judging any assertion.
What practice assertion-reason questions from Genetics and Evolution use the same evaluation method?
Question 1
Statement I: Klinefelter syndrome results from 47, XXY karyotype due to an extra X chromosome.
Statement II: This is an autosomal trisomy similar to Down's syndrome.
Choose the correct option:
A) Both correct
B) Both incorrect
C) I correct, II incorrect
D) I incorrect, II correct
Statement I matches the verified karyotype 47 XXY from an extra sex chromosome. Statement II is false because it is sex-chromosome aneuploidy, not autosomal. The answer is C. Judge each statement against the exact chromosome type.
Question 2
Statement I: Patau syndrome is trisomy 13 and Edwards syndrome is trisomy 18.
Statement II: Both are caused by absence of one sex chromosome like Turner's.
Choose the correct option from A, B, C, D as above.
Statement I is correct on the chromosome numbers. Statement II is incorrect because both Patau and Edwards are autosomal trisomies, not sex-chromosome monosomy. The answer is C. Independent evaluation of autosomal versus sex chromosome decides the option.
If you get stuck on these while revising Genetics and Evolution, search the past-paper archive by chapter to see every similar worked solution.
How do you solve chromosomal disorders assertion-reason questions in 45 seconds for NEET Biology?
Recall exact karyotype numbers for the named syndromes the instant you read them. Write for Down's, for Turner, and for Klinefelter on the margin.
Judge each statement separately against that karyotype. Ignore the other statement until both verdicts are clear.
Match the pattern of correct or incorrect directly to the four options without re-reading the whole question. This sequence fits the 45-second slot and the 90-question Biology paper. The same process appears in the Lac Operon NEET 2026 article for another assertion-reason example from the same chapter: Lac Operon NEET 2026: Only Statement A is Correct.
Why are both statements incorrect in the NEET 2026 chromosomal disorders assertion-reason question?
Statement I confuses sex-chromosome monosomy (Turner) with autosomal trisomy (Down's). The absence of an X chromosome cannot produce trisomy 21. Statement II reverses the actual monosomy of Turner into an additional copy, which matches neither the name nor the karyotype.
Correct option B aligns with the verified chromosomal mechanisms. Attach the exact number and chromosome type to each syndrome name first. That habit lets you evaluate any assertion-reason pair on chromosomal aneuploidies in one read. For any doubt that still lingers, photograph the question to receive a step-by-step solution.
Next step: photograph a doubt on NEET JEEnius AI and photograph any question you are stuck on and get a step-by-step solution across Physics, Chemistry and Biology (20 free a month).
Frequently asked questions
Why are both statements incorrect in the chromosomal disorders NEET 2026 question?
Statement I wrongly attributes Down's syndrome to absence of one X chromosome. Down's is actually autosomal trisomy 21 with 47,+21 karyotype. Statement II wrongly states Turner's syndrome results from an additional copy. Turner's is monosomy X with 45,XO karyotype. This exact swap makes both statements false, so the answer is option B.
What is the karyotype for Turner's syndrome and Down's syndrome?
Turner's syndrome is monosomy X with karyotype 45,XO caused by absence of one sex chromosome. Down's syndrome is trisomy 21 with karyotype 47,+21. Always note the total chromosome count and whether it is autosomal or sex chromosome aneuploidy. This prevents mixing the two syndromes in assertion-reason questions.
How do you solve assertion reason questions on chromosomal disorders for NEET?
Write the exact karyotype beside each syndrome name the moment it appears: 47,+21 for Down's, 45,XO for Turner and 47,XXY for Klinefelter. Judge each statement independently against the verified karyotype. Match the pattern of correct or incorrect directly to the four options. This process takes under 45 seconds.
What is the difference between Down's syndrome and Klinefelter syndrome?
Down's syndrome is autosomal trisomy of chromosome 21 giving 47 chromosomes and affects both sexes equally. Klinefelter syndrome is sex-chromosome aneuploidy with 47,XXY karyotype due to an extra X and occurs only in males. Match the syndrome name to its exact chromosome type and total count before evaluating any assertion.
Is Klinefelter syndrome autosomal or sex chromosome aneuploidy?
Klinefelter syndrome is sex-chromosome aneuploidy with 47,XXY karyotype from an extra X chromosome. It is not autosomal like Down's, Patau or Edwards syndromes which involve chromosomes 1-22. Statement II claiming it is autosomal trisomy similar to Down's is therefore incorrect.