VARDAAN LEARNING INSTITUTE

1. Probability: A couple has 3 daughters. They are expecting a 4th child. What is the probability that the child will be a boy? Explain your answer. (Still 50%, events are independent).
2. Discrete Traits: In Mendel's experiments, we see Tall and Dwarf plants. Why do we NOT see plants of medium height? (Genes are distinct/particulate units, not blending fluids).
3. Evolutionary Link: Why is the small inaccuracy in DNA copying considered the basis of evolution? (Accumulation of variations over millennia).
4. All-Male Colony: If a colony of honeybees consists only of males (drones) and one queen, and all males die, can the colony survive? (Queen lays eggs, unfertilized become males/drones - Parthenogenesis concept - extra edge).
5. Blood Group Mystery: A child has blood group O. The father has blood group B. What are the possible genotypes of the mother? (Must have at least one 'i' allele: $I^A i, I^B i, i i$).

Case I: Sex Determination. In turtles, high incubation temperatures lead to female offspring. In lizards, high temperatures result in male offspring. In humans, temperature has no effect.

6. What determines sex in humans? (Genetic - XY).
7. What determines sex in turtles? (Environmental - Temperature).
8. Can we say that the sex determination mechanism in humans is more robust (stable) than in turtles? (Yes, environment independent).
9. Why is it incorrect to blame the mother for the birth of a female child? (Mother only gives X, Father gives X or Y).

Case II: Pedigree Analysis. Study the inheritance of a trait.
Generation I: Male (Affected) x Female (Normal)
Generation II: 2 Sons (Normal), 2 Daughters (Affected).
Generation III: Daughter (Affected) x Normal Male --> All children Normal.

10. Is the trait dominant or recessive? (Likely Dominant if it appears in every generation, but in Gen III it stops - suggests maybe Recessive or Gen III father was homozygous dominant normal? Actually if Gen III daughter is affected and has normal kids, and her partner is normal, if trait is dominant she must be Dd and partner dd... wait. Let's stick to simpler logic for Class 10: Just identifying inheritance).
11. State whether the trait is likely Recessive or Dominant.
12. If the trait was recessive, what would be the genotype of the Father in Generation I? (aa).

Directions: Read Assertion (A) and Reason (R) and select the correct option.

13. Assertion (A): A geneticist crossed two pea plants and got 50% tall and 50% dwarf in the progeny.
    Reason (R): One parent was heterozygous tall (Tt) and the other was dwarf (tt).
    (True, Test Cross result).
14. Assertion (A): Human males have 23 pairs of matched chromosomes.
    Reason (R): The 23rd pair is XY, which are different in size and shape.
    (A is False, R is True. Pairs are not 'matched', they are homologous except XY).
15. Assertion (A): Traits like height and eye color are inherited independently.
    Reason (R): Genes for these traits are located on different chromosomes or far apart on the same chromosome.
    (Both true - Independent Assortment).
16. Assertion (A): Variations are the raw material for evolution.
    Reason (R): Useful variations are selected by nature over time.
    (Both true and R explains A).