SEX DETERMINATION

Sexual reproduction is the formation of offspring that are genetically distinct from their parent; most often the parent contributes genes to their offspring. Among most eukaryotes, sexual reproduction consists of two processes that lead to an alternation of haploid and diploid cells: meiosis produce haploid gametes and fertilization produces diploid zygotes. The term sex refers to sexual phenotype. Most organisms have only two sexual phenotypes: male and female. The fundamental different between males and females is gamete size: male produce small gametes: female produce relatively large gametes. The mechanism by which sex is established is termed sex determination. Sex determination is a process of sex differentiation which utilizes various genetical concepts to decide whether a particular individual will develop into male or female. We defined the sex of an individual in term of the individual’s phenotype – ultimately, the type of gametes that is produces. Sometimes an individual has chromosome or genes that are normally associated with one sex but a morphology corresponding to the opposite sex. For instance, the cells of female human normally have X chromosomes, and the cells of a males have one X chromosome and one Y chromosome. A few rare persons have male anatomy, although their cells each contain two X chromosome. Even though these people are genetically female, we refer to them as male because their sexual phenotype is male.

There are many ways in which sex differences arise. In some species, both sexes are present in the same individual a condition termed hermphroditism, organisms that bear both male and female reproductive structures are said to be mioecious (meaning “one house”). Species in which an individual has either male or female reproductive structure are said to be dioecious (meaning “two house”). human are dioecious. Among dioecious species, the sex of an individual may be determined chromosomally, genetically, or environmentally.