Dihybrid Cross and 9 to 3 to 3 to 1 Ratio_Unsolved Paper
Chapter: Heredity and Evolution | Topic: Dihybrid Cross and 9 to 3 to 3 to 1 Ratio
DIHYBRID CROSS AND 9 TO 3 TO 3 TO 1 RATIO_UNSOLVED PAPER
Topic: Dihybrid Cross and 9 to 3 to 3 to 1 Ratio
Q1. A cross involving two pairs of contrasting traits is called a:
- Monohybrid cross
- Dihybrid cross
- Test cross
- Back cross
Q2. The classical phenotypic ratio obtained in the F₂ generation of a Mendelian dihybrid cross is:
- 3:1
- 1:1
- 9:3:3:1
- 1:2:1
Q3. A pea plant has the genotype RrYy. Which of the following represents one possible gamete produced by this plant?
- RY
- Rr
- RrY
- RRYy
Q4. In the cross RrYy × RrYy, the offspring can show:
- Only one phenotype
- Two different phenotypes
- Four different phenotype combinations
- Eight different phenotype combinations
Q5. The 9:3:3:1 ratio is associated with the inheritance of:
- One pair of traits only
- Two pairs of traits
- Three pairs of traits
- Only recessive traits
Q6. Which principle is illustrated by the independent inheritance of two different pairs of characteristics in Mendel's dihybrid experiment?
- Law of independent assortment
- Law of conservation
- Law of dominance only
- Law of acquired characteristics
Short questions
Q1. What is a dihybrid cross? How is it different from a monohybrid cross?
Q2. What does the genotype RrYy represent in a dihybrid cross?
Q3. How many different types of gametes can a plant with genotype RrYy produce? Write the possible combinations.
Q4. What does the 9:3:3:1 phenotypic ratio represent in a typical Mendelian dihybrid cross?
Q5. A school garden contains pea plants that differ in both seed colour and seed shape.
Why would studying two characteristics together provide more information than studying only one characteristic?
Q6. A teacher gives students two sets of coloured cards to represent two pairs of alleles and asks them to combine one card from each set to form gametes.
What genetic idea is this activity designed to help students understand?
Q1. Describe Mendel's dihybrid cross using two pairs of contrasting characteristics in pea plants. Explain the significance of the parental generation, F₁ generation, and F₂ generation.
Q2. Explain how the 9:3:3:1 phenotypic ratio can arise in the F₂ generation of a dihybrid cross. Use an appropriate genetic cross or Punnett square to support your explanation.
Q3. Explain the law of independent assortment using a dihybrid cross. Discuss how the inheritance of one pair of characteristics can be considered independently of another pair in Mendel's experiment.
Q1. In a hypothetical dihybrid cross, 160 offspring are obtained. Assume the expected phenotypic ratio is 9:3:3:1.
a) Calculate the expected number of offspring in each of the four phenotypic categories.
b) What total number of offspring is represented by the ratio?
Q2. A student records the following results from a hypothetical dihybrid cross:
a) What ratio do these numbers approximately represent?
b) Which Mendelian dihybrid ratio could be used for comparison?
Q3. A biology teacher asks students to predict the offspring of a cross involving two independently inherited characteristics. The class uses 64 model offspring cards and groups them into four phenotypic categories according to the expected Mendelian ratio.