LIWA

Heredity

CBSE Class 10 · Science · Chapter 8

Past board exam questions

CBSE 2027 sample paper · 4 marks

In order to study patterns of inheritance, Neha had performed typical Mendelian experiments with pea plants in the field. In experiment one, she crossed a pea plant having white flowers (vv) with another pea plant bearing violet flowers (VV). In another experiment, in addition to the colour of the flower she also focussed on the height of the pea plant. This time she crossed a pea plant having violet flowers and tall height (VVTT) with another pea plant having white flowers and short height (vvtt). What percentage is expected for the following traits as a result of these experiments? Give a reason. A. Violet flowers in F1 and F2 generation in experiment one? B. Tall height plants with white flowers in F2 generation in experiment two? C. Percentage of medium height plants with light violet flowers in F1 and F2 generations in experiment two? Give a reason.

Show answer
A. Experiment one: VV × vv. In F1 all plants (100%) are Vv and have violet flowers. F2 (Vv × Vv): 1 VV : 2 Vv : 1 vv, so 75% (3/4) of the plants have violet flowers, because violet flower colour is the dominant trait in pea plants. B. Experiment two: F1 is all VvTt (violet, tall). In F2 (VvTt × VvTt), tall white plants are vvTT or vvTt: probability = 1/4 (vv) × 3/4 (T_) = 3/16 = 18.75% – a combination of one recessive and one dominant trait. C. Zero percent in both F1 and F2. In pea plants no half-way characteristics are produced: even a single copy of T or V produces the same result as two copies, so the plants are either tall or short and either violet or white. No plants with medium …

CBSE 2027 sample paper · 4 marks

In order to study patterns of inheritance, Neha had performed typical Mendelian experiments with pea plants in the field. In experiment one, she crossed a pea plant having white flowers (vv) with another pea plant bearing violet flowers (VV). In another experiment, in addition to the colour of the flower she also focussed on the height of the pea plant. This time she crossed a pea plant having violet flowers and tall height (VVTT) with another pea plant having white flowers and short height (vvtt). What percentage is expected for the following traits as a result of these experiments? Give a reason. A. Violet flowers in F1 and F2 generation in experiment one? B. Tall height plants with white flowers in F2 generation in experiment two? D. Percentage of short height plants with white flowers in F1 and F2 generations in experiment two?

Show answer
A. Experiment one: VV × vv. In F1 all plants (100%) are Vv and have violet flowers. F2 (Vv × Vv): 1 VV : 2 Vv : 1 vv, so 75% (3/4) of the plants have violet flowers, because violet flower colour is the dominant trait in pea plants. B. Experiment two: F1 is all VvTt (violet, tall). In F2 (VvTt × VvTt), tall white plants are vvTT or vvTt: probability = 1/4 (vv) × 3/4 (T_) = 3/16 = 18.75% – a combination of one recessive and one dominant trait. D. F1: zero percent – all F1 plants are VvTt and show only the dominant traits (violet, tall). F2: short white plants must be vvtt (both traits recessive): 1/4 × 1/4 = 1/16 = 6.25%.

CBSE 2026 board paper · 1 mark

Choose the correct statements with reference to chromosomes : (i) carry hereditary information from parents to next generation. (ii) are thread-like structures located inside the nucleus of an animal cell. (iii) always exist in pairs in human gametes. (iv) are involved in the process of cell division.

  1. (i) and (ii)
  2. (iii) and (iv)
  3. (i), (ii) and (iv)
  4. (ii), (iii) and (iv)
Show answer
(i), (ii) and (iv)

CBSE 2026 board paper · 1 mark

The genotype of green stemmed tomato plant is denoted by ‘GG’ and that of purple stemmed tomato plant as ‘gg’. Hybrid of a cross between these two were self-pollinated to obtain F2 progeny. What will be the ratio of GG, Gg and gg in this F2 progeny ?

  1. 2 : 1 : 1
  2. 3 : 1 : 0
  3. 1 : 1 : 2
  4. 1 : 2 : 1
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1 : 2 : 1

CBSE 2026 board paper · 1 mark

Identify the traits that cannot be transmitted from parents to the off-springs : (i) Swimming technique (ii) Blood group (iii) Eye colour (iv) Dancing skills Options :

  1. (i) and (ii)
  2. (i) and (iv)
  3. (iii) and (iv)
  4. (ii) and (iii)
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(i) and (iv)

CBSE 2026 sample paper · 1 mark

In a cross between black furred rabbit (B) and white furred rabbit (b), all offspring were found to have black fur. What can be inferred about the genetic makeup of the parent rabbits?

  1. BB X bb
  2. Bb X Bb
  3. Bb X bb
  4. bb X bb
Show answer
BB X bb

CBSE 2026 board paper · 1 mark

When a human egg is fertilized by a sperm having ‘Y’ chromosome, the zygote has the following combination of chromosomes :

  1. 44 + XX
  2. 22 + XX
  3. 44 + XY
  4. 22 + XY
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44 + XY

CBSE 2026 board paper · 1 mark

Sex is determined by different factors in various species. However, in human beings, it is determined genetically. Which amongst the following option(s) is/are correct for human beings ? (i) Gamete carrying X chromosome from female parent. (ii) Gamete carrying X chromosome from male parent. (iii) Gamete carrying Y chromosome from male parent.

  1. (ii) and (iii)
  2. (i) only
  3. (i) and (iii)
  4. (iii) only
Show answer
(ii) and (iii)