In a eukaryotic cell, the site of ribosomal RNA synthesis is the: MCQ with Answer and Explanation

Explanation:
Pleiotropy occurs when a single gene affects two or more distinct phenotypic traits. This happens because the gene product (protein) may be used in multiple biological pathways or expressed in different tissues. Examples include phenylketonuria (PKU), sickle cell anemia, and Marfan syndrome. Epistasis involves the interaction of different genes, polygenic inheritance involves multiple genes affecting one trait, and incomplete dominance is a single gene interaction.

Explanation:
Ethylene (C₂H₄) is a gaseous hormone that promotes fruit ripening, senescence, and abscission. It is the only gaseous plant hormone.

Explanation:
Meiosis involves two divisions, producing four haploid, genetically diverse cells. Crossing over between homologous chromosomes occurs during prophase I, leading to recombination. Thus, C is correct.