Implantation and Establishment of the Conceptus
Strictly defined, the conception of a new individual occurs at the moment when chromosomes from the male and female pronuclei associate to form the mitotic figure of the first cleavage. Despite the fact that each gamete contributes 23 chromosomes to the zygote, the contributions of egg and sperm to the development of the embryo are not equal in practice. Because the zygote cytoplasm is almost entirely derived from the egg (see section 4.7), all of the embryo’s mitochondrial DNA is therefore maternal. This condition persists for the entire life span of the new individual. In addition other molecules of shorter life such as some RNA and proteins are derived from the egg. Thus much of the metabolic activity and initial behaviour of the zygote depends entirely on molecules of maternal origin.
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- Greep, R. O. (ed.) (1973). ‘Female reproductive system’, in American Handbook of Physiology, sec. 7, Endocrinology, vol. II, pt 2, American Physiological Society, WashingtonGoogle Scholar
- Johnson, M. H. (ed.) (1977). Development in Mammals, North-Holland, AmsterdamGoogle Scholar
- Odell, W. D. and Moyer, D. L. (1971). Physiology of Reproduction, C. V. Mosby Co., St LouisGoogle Scholar