Question

(a) What are maternal-effect genes? (b) When are gene products from these genes made, and where are they located? (c) What aspects of development do maternal-effect genes control? (d) What is the phenotype of maternal-effect mutations?

Short answer

Answer: Maternal-effect genes are genes whose expression in the mother influences the development of the offspring, often by affecting events in early embryogenesis. These gene products are typically made during oogenesis (egg development) in the mother and stored in the egg cytoplasm, which means their initial location is within the developing embryo. Maternal-effect genes control various aspects of early development such as spatial organization, determination of body axes (anterior-posterior, dorsal-ventral), and the formation of body segments in the offspring. Mutations in maternal-effect genes may not result in noticeable phenotypic alterations in the mother but can cause developmental defects or even lethality in the offspring due to the influence of the mutated gene product on embryogenesis.

Step-by-step solution

(a) Definition of maternal-effect genes)

(Maternal-effect genes are genes whose expression in the mother influences the development of the offspring, often by influencing events in early embryogenesis.)

(b) Timing and location of gene products)

(Gene products from maternal-effect genes are typically made during oogenesis (egg development) in the mother, and they are stored in the egg cytoplasm. Therefore, their initial location is within the developing embryo.)

(c) Developmental aspects controlled by maternal-effect genes)

(Maternal-effect genes control various aspects of early development such as spatial organization, determination of body axes (anterior-posterior, dorsal-ventral), and the formation of body segments in the offspring.)

(d) Phenotype of maternal-effect mutations)

(The phenotype of maternal-effect mutations is often observed in the offspring. When a mutation in a maternal-effect gene occurs, the mother herself may not show any noticeable phenotypic alteration, but the offspring of the affected mother may exhibit developmental defects or even lethality due to the influence of the mutated gene product on embryogenesis.)