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Science · 2025 · 3 marks
CBSE 2025 · Region 6 · Set 1 · Q30
The gene combination of purple flowered pea plants is denoted as (WW) and that of white flowered pea plants as (ww), when these two plants are…
The gene combination of purple flowered pea plants is denoted as (WW) and that of white flowered pea plants as (ww), when these two plants are crossed $\displaystyle \mathrm{F}_{1}$ generation is obtained.
(a)
List two observations made by Mendel in $\displaystyle \mathrm{F}_{1}$ generation plants.
(b)
Give the (i) percentage of white flowered plants and (ii) ratio of the gene combinations WW, Ww and ww in $\displaystyle \mathrm{F}_{2}$ generation.
(c)
Write one difference between dominant and recessive trait.
Marking-scheme solution
(a) All plants were purple flowered/ No mixed coloured flowers were observed / No white flowered plants were observed / Only dominant parental trait was observed.
(b) (i) $\displaystyle 25$%
(ii) $\displaystyle 1$ : $\displaystyle 2$ : $\displaystyle 1$ / \(\displaystyle 1 \mathrm{WW}: 2 \mathrm{Ww}: 1 \mathrm{ww}\)
(c)
| Dominant Trait | Recessive Trait |
| A trait that can express itself in the presence of its unexpressed contrasting trait / Trait express itself always | A trait that remains unexpressed in the presence of its contrasting form. |
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CBSE Class 10 Science past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.