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Biology · 2024 · 3 marks
CBSE 2024 · Region 2 · Set 1 · Q23
(a) (i) Write the karyotype and the genetic disorder of an individual who has developed from a zygote formed from an 'XX' egg fertilised by a 'Y'…
(a)(i)
Write the karyotype and the genetic disorder of an individual who has developed from a zygote formed from an 'XX' egg fertilised by a 'Y' sperm.
(ii)
Mention any two symptoms of this genetic disorder.
(iii)
Write the possible reason that leads to the formation of this 'XX' egg.
OR
(b)
In case of any dispute, a very small sample of tissue or even a drop of blood can help us to determine the paternity of a child. Provide a scientific explanation to substantiate the statement.
Marking-scheme solution
(i)
• Karyotype - $\displaystyle 44$ + XXY/$\displaystyle 47$-XXY/AA+XXY,
• Genetic disorder - Klinefelter’s syndrome
(ii)
Gynaecomastia/development of breast, Sterile Individuals, , overall masculine
development
(iii)
Failure of segregation of chromatids or chromosomes/non-disjunction of chromatids or
chromosomes during cell division or gametogenesis.
DNA fingerprinting is the basis of paternity testing, high degree of polymorphism in
DNA, the polymorphisms are inheritable.
Isolation of DNA and amplification by PCR, Digestion of DNA, Separation of DNA fragments by electrophoresis, blotting and hybridisation, detection of hybridised fragments by autoradiography, matching the DNA bands of father and child.
All Molecular Basis of Inheritance questions2024 question paperNCERT solutions: Molecular Basis of InheritancePractice Molecular Basis of Inheritance →
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CBSE Class 12 Biology past-paper question from the 2024 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.