CBSE 2025 · Region 1 · Set 2 · Q32 · 3 marks
In one of Mendalian experiments, when $\displaystyle \mathrm{F}_{1}$ generation pea plants with round yellow seeds were self-pollinated, pea seeds with the following combinations were obtained in $\displaystyle \mathrm{F}_{2}$ generation : Seeds Round yellow Round green Wrinkled yellow Wrinkled green Number $\displaystyle 800$ $\displaystyle 275$ $\displaystyle 268$ $\displaystyle 90$
Analyse the result and describe the mechanism of inheritance of traits which explains the above results.
| Seeds | Round yellow | Round green | Wrinkled yellow | Wrinkled green |
| Number | $\displaystyle 800$ | $\displaystyle 275$ | $\displaystyle 268$ | $\displaystyle 90$ |
Marking-scheme solution
Calculation of ratio of Seeds as per data given.
Round and yellow \(\displaystyle -\frac{\mathbf{8 0 0}}{\mathbf{9 0}}=9\),
Round and green \(\displaystyle -\frac{\mathbf{2 7 5}}{\mathbf{9 0}}=3\)
Wrinkled and yellow \(\displaystyle -\frac{\mathbf{2 6 8}}{\mathbf{9 0}}=3\) Wrinkled and green \(\displaystyle -\frac{90}{90}=1\)
Parents -
Round and Yellow Wrinkled and Green
RRYY × rryy Gametes
Gamete - RY/Ry/rY/ry
\[F_{2}-9: 3: 3: 1
\]
Round yellow - \(\displaystyle 9 \mid\) Round green - $\displaystyle 3$ Wrinkled yellow - $\displaystyle 3$ Wrinkled green - $\displaystyle 1$Appearance of new combinations of characteristics show that traits for Round/Wrinkled and Yellow/Green seeds are independently inherited/ Independent inheritance of two separate traits.
HeredityMonohybrid and Dihybrid CrossesAnalyseshort_answerhard
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CBSE Class 10 Science past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.