Section A: Dihybrid Cross
- Define Dihybrid Cross. What is the ratio obtained in the F2 generation?
- Mendel crossed Round Yellow (RRYY) seeds with Wrinkled Green (rryy) seeds.
(a) What are the gametes of P generation?
(b) Write the phenotype of F1 progeny.
(c) Which law does this experiment demonstrate?
- How many types of gametes are produced by a plant with genotype RrYy? Name them. (RY, Ry, rY, ry).
- In a dihybrid cross of 1600 plants, how many are expected to be Round-Green? (3/16 * 1600 = 300).
- State the Law of Independent Assortment. How is it derived from the dihybrid cross?
Section B: Mechanism of Heredity
- Mechanism: How do genes control traits? Explain with the example of plant height
(Growth Hormone enzyme efficiency).
- What would happen if the gene 'T' was altered to produce an enzyme that works very slowly? (Less
hormone --> Dwarf).
- How does the chromosome number remain constant generation after generation? (Meiosis halving +
Fertilization doubling).
- Is it possible that a trait is inherited but not expressed? Explain with an example. (Recessive
traits).
- "DNA is the information source for making proteins." If the information is changed, what is the
sequence of effects?
Section C: Blood Group Genetics
- A man with blood group A marries a woman with blood group O and their daughter has blood group O.
(a) Is this information enough to tell which trait is dominant?
(b) Determine the genotype of the man. ($I^A i$).
- A child has blood group O. If the father has blood group A and mother has blood group B, work out
the genotypes of the parents. ($I^A i$ and $I^B i$).
- What are the possible blood groups of offspring if both parents are AB type? (A, B, AB).
- Explain the concept of Co-dominance using AB blood group as an example.
- Can two O blood group parents have a child with blood group A? Justify. (No, ii + ii = ii).
