what is zygote?how is it formed?
Answers
Answer:
Zygote, fertilized egg cell that results from the union of a female gamete (egg, or ovum) with a male gamete (sperm). ... In the embryonic development of humans and other animals, the zygote stage is brief and is followed by cleavage, when the single cell becomes subdivided into smaller cells.
DEFINITION OF ZYGOTE
☛ A zygote is the first diploid cell that is formed by the fusion of male and female gametes resulting in the formation of an embryo.
➵ REMEMBER POINTS
- The zygote stage development occurs in the first week of fertilization.
- The genome of the zygote is the combination of DNA in each gamete and contains all the genetic information required to form an individual.
- A zygote is a fertilized ovum.
- The germ cells undergo meiosis to reach a haploid state (n) as part of spermatogenesis and oogenesis.
- The sperm and the unfertilized ovum reínstates a chromosome set in zygote in a diploid state (2n).
FORMATION OF ZYGOTE
➛ Fertilization is always initiated with attachment of sperm with zona pellucida (found around an egg), then acrosome of sperm release an enzyme which digest the zons pellucid, and then the head of sperm penetrates into the plasma membrane of egg or oocyte and sperm nucleus passes into the cytoplasm.
➛ Within the oocyte, the haploid set of sperm and egg chromosome are initially separated from each other and constitute respectively the male and female pronuclei.
➛ They subsequently fuse to form a diploid nucleus, this fertilized egg is known as the zygote.
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EXTRA POINTS
⑴ Zygote represents itself as a single cell with diploid set of chromosomes.
⑵ Further zygote is divided for development into smaller cells called blastomeres (a group of cells is called blastocysts).
⑶ After a few five days of fertilization, blastocysts move toward the uterus from the fallopian tube, and attached tightly to the uterine epithelium such phenomenon is called implantation.