In order to understand how the process of fertilization and the birth of a new life, you need to familiarize yourself with the basic concepts.It is necessary to deal with the fact that such a zygote.And to answer other questions about how it is formed, which has specific features, what are the stages of its further development, which may prevent it.
Let's start from the beginning, to answer the first question.What is a zygote?This cell, which is formed by the merger of the two parental germ cells in a process called fertilization.It is characteristic of heterosexual organisms used for breeding them.The living beings who have formed zygote, include not only people and animals, but also many plants and fungi.The term has entered a botanist Eduard Strasburger from Germany in the late 19th century.
understand what a zygote, remember what characterized the cells that form it.The sex cells, or gametes, are produced by special bodies (sex), they are characterized by the presence of single (haploid) set of chromosomes.As we have learned, the formation of the zygote is the result of the union of two gametes, which means that it contains a double (diploid) set of carrier DNA.Unique cell, giving rise to a new organism, scientists on the definition, is totipotent.That is, it is able to produce absolutely any cell of the body.What else is interested in this cellular structure?The zygote is divided at first did not like a regular cell.Before divisions no growth stage, and eventually every subsequent daughter cells are smaller than the previous ones.As a result of successive splits, the ovum becomes like mulberries.
If we consider the entire development process of the embryo as a whole, it is possible to answer the question of what a zygote is as follows.She is one of the stages of its development.The first step in this case is considered gametes and the subsequent steps have characterized the successive changes in the zygote.Here are the successive levels of embryonic differentiation.Next, after the zygote stage - morula (has a cavity structure) followed blastula (single embryo), the gastrula (three-layered embryo) finally neurula, which smoothly passes into organogenesis.
By the way, note the interesting point: the zygote stage to a living organism may be delayed.This happens in fungi and algae.After fertilization and the formation of a diploid cell it becomes stationary and is stored for a long time.In this case, the cage call zygospore.In humans, a rest period is only thirty hours.At this time, the future embryo moves through the fallopian tube into the uterus, where the passage of time there will ovum implanting in the lining.Disrupts the normal flow of the process itself and the further development of the zygote may be negative factors such as mutations at the level of individual genes or entire chromosomes, woman drinking alcohol, narcotic drugs, certain medications, smoking, viral diseases.
