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Class 10  »  Biology  »  Heredity and Evolution

Monohybrid Cross and 3 to 1 Ratio_Unsolved Paper

Class 10

Chapter: Heredity and Evolution | Topic: Monohybrid Cross and 3 to 1 Ratio

Unsolved Paper
Study Material.
Class 10

MONOHYBRID CROSS AND 3 TO 1 RATIO_UNSOLVED PAPER

Topic: Monohybrid Cross and 3 to 1 Ratio

Time: 90 mins | Marks: 45 | Difficulty: Medium
multiple choice questions

Q1. A cross involving the inheritance of one pair of contrasting characteristics is called a: 

  1. Dihybrid cross
  2. Monohybrid cross
  3. Test cross
  4. Reciprocal cross

Q2. In a typical Mendelian monohybrid cross, the phenotypic ratio observed in the F₂ generation is:

  1. 1:1
  2. 2:1
  3. 3:1
  4. 9:3:3:1

Q3. If T represents the allele for tallness and t represents the allele for dwarfness, which genotype represents a heterozygous tall pea plant?

  1. TT
  2. tt
  3. Tt
  4. TTT

Q4. Which of the following represents the phenotype of a pea plant with genotype tt?

  1. Tall
  2. Both tall and dwarf
  3. Dwarf
  4. Neither tall nor dwarf

Q5. In the cross Tt × Tt, the possible genotypes of the offspring include:

  1. TT, Tt and tt
  2. TT only
  3. Tt only
  4. TT and tt only

Q6. The 3:1 ratio in a monohybrid cross refers to the ratio of:

  1. Male to female offspring
  2. Dominant phenotype to recessive phenotype
  3. Homozygous to heterozygous offspring
  4. Parents to offspring

Short questions

Q1. What is a monohybrid cross? Why is it called a "mono" hybrid cross?

Q2. Differentiate between genotype and phenotype with reference to a pea plant.

Q3.What is meant by a homozygous condition? Give the possible genotype for a homozygous tall pea plant if T represents tallness. 

Q4. What is meant by a heterozygous condition? Write the genotype of a heterozygous pea plant showing the dominant trait.

Q5. Students in a school garden observe tall and dwarf pea plants among the offspring of a cross.

Why might both forms appear in the second generation even when one trait was not visible in the first generation?

Q6. Suppose a student uses coloured beads to represent the two alleles carried by a parent plant.

Why would two different beads be useful for representing a heterozygous condition?

long questions

Q1. Describe a monohybrid cross between a pure tall pea plant and a pure dwarf pea plant. Explain the significance of the parental generation, F₁ generation, and F₂ generation in this experiment.

Q2. Explain how the 3:1 phenotypic ratio arises in the F₂ generation of a monohybrid cross. Use a suitable genetic cross to support your explanation.

Q3.Explain the relationship between genotype and phenotype using the cross Tt × Tt. Discuss the possible combinations of alleles and how they relate to the observable characteristics of the offspring. 

application-based questions

Q1. In a monohybrid cross, 160 offspring are produced and the expected phenotypic ratio is 3:1.

a) Calculate the expected number of offspring showing the dominant phenotype.
b) Calculate the expected number showing the recessive phenotype.

Q2. A student records the following results from an experiment:

Phenotype

Number of Plants

Tall

75

Dwarf

25

a) Calculate the ratio of tall plants to dwarf plants.
b) Compare the observed ratio with the expected Mendelian monohybrid ratio.

Q3. A biology teacher gives students 80 model offspring cards from a hypothetical monohybrid cross. The expected phenotypic ratio is 3:1.

a) How many cards should theoretically represent the dominant phenotype?
b) How many should represent the recessive phenotype?

Total: 45 Marks | Time: 90 mins

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Heredity Definition and Mendels Work Dihybrid Cross and 9 to 3 to 3 to 1 Ratio Dominant and Recessive Traits Sex Determination in Humans Variations Importance and Causes Evolution Darwins Theory Natural Selection Speciation Molecular Evidence for Evolution Homologous and Analogous Organs Fossils and Their Significance Human Evolution