maternal sex determination

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• Maternal influence on sex determination — In humans and several other species of animals, the father determines the sex of the child. In the XY sex determination system, the female provided ovum contributes an X chromosome and the male provided sperm contributes either an X chromosome or …   Wikipedia

• XY sex-determination system — Drosophila sex chromosomes The XY sex determination system is the sex determination system found in humans, most other mammals, some insects (Drosophila) and some plants (Ginkgo). In this system, females have two of the same kind of sex… …   Wikipedia

• X0 sex-determination system — The X0 sex determination system is a system that grasshoppers, crickets, cockroaches, and some other insects use to determine the sex of their offspring. In this system, there is only one sex chromosome, referred to as X. Males only have one X… …   Wikipedia

• Sex allocation — is the allocation of resources to male versus female reproduction in sexual species (Charnov 1982). Sex allocation depends upon the breeding system of a species, as well as how reproduction is carried out within each breeding system. Breeding… …   Wikipedia

• Sex ratio — is the ratio of males to females in a population. The primary sex ratio is the ratio at the time of conception, secondary sex ratio is the ratio at time of birth, and tertiary sex ratio is the ratio of mature organisms. [Nancy S. Coney and W. C.… …   Wikipedia

• sex — /seks/, n. 1. either the male or female division of a species, esp. as differentiated with reference to the reproductive functions. 2. the sum of the structural and functional differences by which the male and female are distinguished, or the… …   Universalium

• Maternal effect — This article concerns the legitimate scientific concept of genes that are expressed only when carried by the female parent. It is not to be confused with the generally discredited theory of maternal impression. A maternal effect is a situation… …   Wikipedia

• Human sex ratio — In anthropology and demography, the human sex ratio is the sex ratio for Homo sapiens (i.e. the ratio of males to females in a population). Like most sexual species, the sex ratio is approximately 1:1. In humans the secondary sex ratio (i.e. at… …   Wikipedia

• Preimplantation genetic diagnosis — In medicine and (clinical) genetics preimplantation genetic diagnosis (PGD) (or also known as Embryo Screening) refers to procedures that are performed on embryos prior to implantation, sometimes even on oocytes prior to fertilization. PGD is… …   Wikipedia

• Sexual differentiation — This article is about the development of sexual dimorphisms in humans. For sex differences for all animals, see Sexual dimorphism. Sexual differentiation is the process of development of the differences between males and females from an… …   Wikipedia

• human embryology — ▪ biology Introduction       the process encompassing the period from the formation of an embryo, through the development of a fetus, to birth.       The human body, like that of most animals, develops from a single cell produced by the union of… …   Universalium