zygotecell
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development
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animals development
...of the diploid parents; gametes from the two parents immediately reunite to form a diploid embryo, without an intervening haploid generation. The male sperm fertilizes a female ovum to form the zygote, which immediately begins to divide into many smaller cells (cleavage). The embryos of animals that lay their eggs on land, such as reptiles and birds, are nourished by a yolk throughout...
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cellular differentiation zoology
...mechanisms were considered essentially to be the basis for growth, differentiation, and morphogenesis, or molding of parts. The distribution of the newly formed cells of the rapidly dividing zygote (fertilized egg) was precisely followed to provide detailed accounts not only of the time and mode of germ layer formation but also of the contribution of these layers to the differentiation...
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division into blastomeres human embryology
The onset of mitosis (ordinary cell proliferation by division) in the activated zygote is a first step toward development in the ordinary sense of that term, and the cells so produced are the first external sign of future body building. To this end, the relatively enormous zygote directly subdivides into many smaller cells of conventional size, suitable as early building units for the future...
reproduction
( in reproduction: Reproduction of organisms )In the sexual reproduction of all organisms except bacteria, there is one common feature: haploid, uninucleate gametes are produced that join in fertilization to form a diploid, uninucleate zygote. At some later stage in the life history of the organism, the chromosome number is again reduced by meiosis to form the next generation of gametes. The gametes may be equal in size (isogamy), or one...
in pregnancy: Initiation of pregnancy )After the chromosomes merge and divide in a process termed mitosis, the...
- multiple birth multiple birth
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multiple birth multiple birth
...developed as a singleton (the three constituting DZ triplets); or from three separate zygotes (trizygotic, or TZ, triplets). Similarly, quadruplets may originate from one up to four zygotes, and quintuplets may derive from one to five zygotes. After being carefully studied, the Canadian Dionne quintuplets (born in 1934) were shown to be a one-zygote set.
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multiple births multiple birth
As with twins, the other types of multiple births may or may not be monozygotic. Any combination may occur; e.g., triplets may be derived from a single zygote (MZ triplets); from two zygotes, one of which divided to produce MZ twins while the other developed as a singleton (the three constituting DZ triplets); or from three separate zygotes (trizygotic, or TZ, triplets). Similarly, quadruplets...
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multiple birth multiple birth
...one of which divided to produce MZ twins while the other developed as a singleton (the three constituting DZ triplets); or from three separate zygotes (trizygotic, or TZ, triplets). Similarly, quadruplets may originate from one up to four zygotes, and quintuplets may derive from one to five zygotes. After being carefully studied, the Canadian Dionne quintuplets (born in 1934) were shown to...
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