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The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. The sexual fusion of haploid cells is called karyogamy , the result of which is the formation of a diploid cell called the zygote or zygospore.
After MZT the diploid embryo takes over genetic control. [1] [2] This requires both zygotic genome activation (ZGA) and degradation of maternal products. This process is important because it is the first time that the new embryonic genome is utilized and the paternal and maternal genomes are used in combination (ie. different alleles will be ...
As the zygote divides, it first becomes the embryo (which means 'growing within'), typically between zero and eight weeks, then from the eighth week until birth, it is considered the fetus (which means 'unborn offspring'). The internal genitalia are all the accessory glands and ducts that connect the gonads to the outside environment.
After the pollen tube enters the gametophyte, the pollen tube nucleus disintegrates and the two sperm cells are released; one of the two sperm cells fertilises the egg cell (at the bottom of the gametophyte near the micropyle), forming a diploid (2n) zygote. This is the point when fertilisation actually occurs; pollination and fertilisation are ...
Animals have life cycles with a single diploid multicellular phase that produces haploid gametes directly by meiosis. Male gametes are called sperm, and female gametes are called eggs or ova. In animals, fertilization of the ovum by a sperm results in the formation of a diploid zygote that develops by repeated mitotic divisions into a diploid ...
7) The diploid zygote which has just been fertilized by the union of haploid egg and sperm during sex. 8) Cells of the diploid structure quickly undergo meiosis to produce spores containing the meiotically halved number of chromosomes, restoring haploidy. These spores express either the mother's dominant gene or the father's recessive gene and ...
Once fertilized, the ovum becomes a single diploid cell known as a zygote. The zygote undergoes mitotic divisions with no significant growth (a process known as cleavage) and cellular differentiation, leading to development of a multicellular embryo [2] after passing through an organizational checkpoint during mid-embryogenesis. [3]
The pronuclei then fuse together in a well regulated process known as karyogamy. This creates a diploid cell known as a zygote, or a zygospore, [4] which can then enter meiosis, a process of chromosome duplication, recombination, and cell division, to create four new haploid gamete cells. One possible advantage of sexual reproduction is that it ...