During early embryo development certain genes are active only if they come from the sperm, while others are active if they come from the egg. This phenomenon is as a result of: A. dosage compensation B. chromosome inactivation C. gene activation D. genomic imprinting Although normal female cells have two X-chromosomes and normal male cells have only X-chromosome, male and female cells have equal X-encoded gene products. This equalization is due to which of the following: A. genomic imprinting B. sex determination C. dosage compensation D. presence of the Y-chromosome in males that is absent E. none of the above A certain tissue B produces a signal that is received by receptors on the surface of the same tissue B thereby causing it to act on its own signal. This type of cell-cell interaction is known as: A. reciprocal interaction B. instructive interaction C. permissive interaction D. epithelial-mesenchymal interaction E. none of the above Fertilization is followed by rapid mitotic cell divisions generally known as _____ that result in production of progressively small cells known as _____. A. gastrulation, organs B. meiosis, sperms C. cleavage, blastomeres D. cleavage, three germ layers E. none of the above If 10 diploid spermatogonia undergo complete and normal gametogenesis, _____ number of cells are formed each with _____ number of chromosomes. A. 4, 46 B. 2, 23 C. 8, 46 D. 10, 23 E. 16, 23