CBSE 2025 · Region 1 · Set 1 · Q19 · 2 marks
Study the cross given below :
Identify the abnormalities '$\displaystyle 1$' and '$\displaystyle 2$' in the offsprings of a cross done between a couple and distinguish between them.
Marking-scheme solution
$\displaystyle 1$ = Klinefelter's Syndrome ($\displaystyle 44$ + XXY)
$\displaystyle 2$ = Turner's Syndrome ($\displaystyle 44$ + XO)
| Klinefelter's Syndrome | Turner's Syndrome |
| Presence of an extra copy of X chromosome / total $\displaystyle 47$ chromosomes / Trisomy of sex chromosomes | Absence of one of the X chromosome / total $\displaystyle 45$ chromosomes / monosomy of sex chromosomes |
| Sterile male | Sterile female |
| Overall masculine development with feminine features / Gynaecomastia or development of breast / tall statured | Rudimentary ovaries / lack of secondary sexual characters / short stature / underdeveloped feminine character |
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CBSE Class 12 Biology past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.