Mendel's Laws of Inheritance — Homi Bhabha Class 9 Biology MCQs with Solutions
Free Homi Bhabha Class 9 Biology Mendel's Laws of Inheritance MCQs with step-by-step solutions (17 questions). Part of Heredity & Genetics. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Mendel's Laws of Inheritance · medium · theory
The scientist regarded as the "Father of Genetics", who worked on pea plants, is:
A. Watson
B. Gregor Mendel ✓ Correct
C. Louis Pasteur
D. Charles Darwin
Solution: Gregor Mendel established the laws of inheritance through experiments on garden pea plants.
Q2 — Mendel's Laws of Inheritance · hard · theory
A trait that appears in the first generation (F₁) and masks the other is called:
A. acquired
B. dominant ✓ Correct
C. recessive
D. hybrid
Solution: The dominant trait is expressed in the F₁ generation, masking the recessive one.
Q3 — Mendel's Laws of Inheritance · medium · theory
A trait that remains hidden in the F₁ generation is called:
A. mutant
B. acquired
C. recessive ✓ Correct
D. dominant
Solution: The recessive trait does not appear in F₁ but can reappear later.
Q4 — Mendel's Laws of Inheritance · hard · theory
When a pure tall pea plant (TT) is crossed with a pure dwarf plant (tt), the F₁ offspring are all:
A. medium height
B. tall (Tt) ✓ Correct
C. half tall, half dwarf
D. dwarf (tt)
Solution: All F₁ plants are Tt and appear tall, since tallness (T) is dominant.
Q5 — Mendel's Laws of Inheritance · hard · theory
In Mendel's monohybrid cross, the phenotypic ratio obtained in the F₂ generation is:
A. 2 : 1
B. 1 : 1
C. 3 : 1 ✓ Correct
D. 9 : 3 : 3 : 1
Solution: Self-pollinating the F₁ (Tt) gives a 3 : 1 ratio of dominant to recessive in F₂.
Q6 — Mendel's Laws of Inheritance · medium · theory
The genetic makeup of an organism (e.g. Tt) is called its:
A. chromosome
B. phenotype
C. genotype ✓ Correct
D. gene pool
Solution: Genotype is the set of alleles (e.g. Tt); phenotype is the visible expression.
Q7 — Mendel's Laws of Inheritance · hard · theory
The observable characteristics of an organism (e.g. its height or flower colour) are called its:
A. chromosome
B. phenotype ✓ Correct
C. genotype
D. allele
Solution: Phenotype refers to the visible traits produced by the genotype and environment.
Q8 — Mendel's Laws of Inheritance · hard · theory
A plant with the genotype Tt is described as:
A. heterozygous (hybrid) tall ✓ Correct
B. pure dwarf
C. homozygous tall
D. homozygous dwarf
Solution: Tt has two different alleles, so it is heterozygous (a hybrid), and it appears tall.
Q9 — Mendel's Laws of Inheritance · medium · theory
Mendel chose the garden pea for his experiments partly because it has:
A. clearly contrasting characters and a short life cycle ✓ Correct
B. no seeds
C. no flowers
D. a very long life cycle
Solution: Pea plants show clear contrasting traits, are easy to cross and grow quickly.
Q10 — Mendel's Laws of Inheritance · hard · theory
Mendel's law of segregation states that during gamete formation, the two alleles of a trait:
A. separate so that each gamete gets only one ✓ Correct
B. both go into every gamete
C. disappear
D. always stay together
Solution: Each gamete receives only one allele of a gene, which recombine at fertilisation.
Q11 — Mendel's Laws of Inheritance · easy · theory
Gregor Mendel carried out his famous inheritance experiments using which plant?
A. Rose
B. Maize
C. Garden pea ✓ Correct
D. Sunflower
Solution: Mendel used the garden pea (Pisum sativum). It was ideal because it has clear contrasting traits, is easy to grow, and can be both self-pollinated and cross-pollinated in a controlled way.
Q12 — Mendel's Laws of Inheritance · easy · theory
An organism that carries two identical alleles for a trait (for example TT or tt) is said to be:
A. Codominant
B. Recessive-only
C. Homozygous ✓ Correct
D. Heterozygous
Solution: Two identical alleles (TT or tt) make an organism homozygous for that trait. When the two alleles are different (Tt), the organism is heterozygous.
Q13 — Mendel's Laws of Inheritance · medium · numerical
In a monohybrid cross between two heterozygous tall pea plants (Tt × Tt), what is the expected phenotypic ratio of tall to short plants in the offspring?
A. 2 : 1
B. 1 : 1
C. 9 : 7
D. 3 : 1 ✓ Correct
Solution: Tt × Tt gives genotypes 1 TT : 2 Tt : 1 tt. TT and Tt are tall (3 plants) and tt is short (1 plant), so the phenotypic ratio is 3 tall : 1 short. (1 : 2 : 1 is the genotypic ratio.)
Q14 — Mendel's Laws of Inheritance · medium · numerical
In the cross Tt × Tt, what fraction of the offspring are expected to be homozygous recessive (tt)?
A. 1/3
B. 1/4 ✓ Correct
C. 1/2
D. 3/4
Solution: The genotypic ratio of Tt × Tt is 1 TT : 2 Tt : 1 tt, a total of 4 parts. The tt (homozygous recessive) is 1 out of these 4 parts, so the fraction is 1/4.
Q15 — Mendel's Laws of Inheritance · medium · theory
In a monohybrid cross every plant of the F1 generation showed only the dominant trait, even though the two parents differed. Which of Mendel's principles best explains this?
A. Law of Use and Disuse
B. Law of Dominance ✓ Correct
C. Law of Limiting Factors
D. Law of Independent Assortment
Solution: The Law of Dominance states that when two different alleles are present, only the dominant one is expressed. This is why all F1 plants show the dominant trait while the recessive allele stays hidden.
Q16 — Mendel's Laws of Inheritance · hard · numerical
In a dihybrid cross between plants heterozygous for both seed shape and seed colour (RrYy × RrYy), 1600 offspring are produced. About how many are expected to show both recessive traits (wrinkled and green)?
A. 100 ✓ Correct
B. 300
C. 900
D. 400
Solution: In a dihybrid F2 the phenotypic ratio is 9 : 3 : 3 : 1, so the double-recessive class is 1/16 of the offspring. 1/16 × 1600 = 100 plants. (900 would be the double-dominant 9/16 group.)
Q17 — Mendel's Laws of Inheritance · hard · theory
A tall pea plant is crossed with a short (tt) plant. The offspring are about one-half tall and one-half short. What is the genotype of the tall parent?
A. tt (homozygous recessive)
B. A tall plant cannot give any short offspring
C. TT (homozygous dominant)
D. Tt (heterozygous) ✓ Correct
Solution: This is a test cross. If the tall parent were TT, all offspring would be tall. A 1 tall : 1 short ratio means the tall parent must carry a hidden recessive allele, so its genotype is Tt (heterozygous).