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Science · 2026 · 3 marks
CBSE 2026 · Region 4 · Set 3 · Q13
Use the following information for Pea plants: Dominant allele for tall plants - T Recessive allele for short plants - t Dominant allele for purple…
Use the following information for Pea plants : Dominant allele for tall plants - T Recessive allele for short plants - t Dominant allele for purple flowers - P Recessive allele for white flowers - p
(a)
Perform a cross between pure plant dominant for both the traits with another plant which is recessive for both the traits and work out the progeny upto $\displaystyle \mathrm{F}_{2}$ generation.
(b)
What is the probability of obtaining tall plants with white flowers in $\displaystyle \mathrm{F}_{2}$ progeny?
Marking-scheme solution
(a)
| Parents: | TTPP | X | ttpp |
| tall purple | short white |
Gametes: TP tp
| ↓ | ||
| \(\displaystyle \mathrm{F}_{1}\) | TtPp | |
| Selfing of \(\displaystyle \mathrm{F}_{1}\) | ||
| TtPp | × | TtPp |
\(\displaystyle \mathrm{F}_{2}\)
| gametes | TP | Tp | tP | tp |
| TP | TTPP | TTPp | TtPP | TtPp |
| Tp | TTPp | TTpp | TtPp | Ttpp |
| tP | TtPP | TtPp | ttPP | ttPp |
| tp | TtPp | Ttpp | ttPp | ttpp |
tall and purple : $\displaystyle 9$
tall and white : $\displaystyle 3$
short and purple : $\displaystyle 3$
short and white : $\displaystyle 1$
(b)
In \(\displaystyle \mathrm{F}_{2}\) progeny probability of Tall, White = $\displaystyle 3$/$\displaystyle 16$
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CBSE Class 10 Science past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.