Question

“Proteins control the expression of various characters.” Explain this statement by taking the example of “tallness” as a characteristic in plants.

Answer 1

Proteins play a crucial role in controlling the expression of various characteristics by acting as enzymes, structural components, or signaling molecules. The characteristic of tallness in plants can be explained by understanding how proteins influence gene expression.

Explanation Using Tallness in Plants:

1. Genes and Proteins

   • A gene is a segment of DNA that contains instructions for making a specific protein.
   • The tallness trait in plants is controlled by a gene that produces a specific protein responsible for growth.

2. Role of Gibberellins and Enzymes

   • In pea plants (Pisum sativum), tallness is influenced by the gibberellin hormone.
   • The gene responsible for tallness encodes an enzyme that helps synthesize gibberellins.
   • If the gene is functional (dominant allele T), it produces sufficient gibberellins, leading to elongation of stem cells and tall plants.

3. Effect of Mutations or Recessive Alleles

   • If there is a mutation in the gene, it may produce a non-functional protein or no protein at all.
   • In such cases (tt genotype), gibberellin synthesis is reduced or absent, leading to short plants (dwarfism).

Answer 2

1. Proteins operate as enzymes, hormones, and structural components, influencing characteristics significantly.
2. DNA genes instruct the production of certain proteins, influencing trait expression.
3. In pea plants, tallness (T) is determined by a dominant gene. This gene generates a protein that modulates gibberellins, a plant hormone that promotes stem elongation.
4. If the dominant allele (T) is present, gibberellin production increases, resulting in a taller plant.
5. If the recessive gene (t) is present, gibberellin production is reduced, resulting in a shorter plant.