236:, and subsequently polarize along the apical-basal axis. This polarization permanently changes the morphology of these cells, and starts the differentiation process. After this, the 8-cell blastomere mass begins to compact by forming tight junctions between themselves, and cytosolic components of the cell accumulate in the apical region while the nucleus of each cell moves to the basal region. The adhesive lateral junction is then formed, and the blastomere is flattened to establish the apical cortical domain. Once the transition begins to a 16-cell mass, the apical cortical domain disappears, but elements of polarity are preserved. This allows for approximately half of the blastomeres to inherit polar regions that can rebuild the apical cortical domain. The other blastomeres that differentiate, then, will become apolar. Polar blastomere cells that differentiate will move to an outer position in the developing
264:
perpendicular to the apical-basal axis, or asymmetrically, meaning horizontal to the apical-basal axis. Many potential hypotheses and conjectures that attempt to explain why these cells orient themselves the way that they do. Some researchers have stated that early-dividing blastomeres tend to divide asymmetrically, while others have proposed that the orientation of 8-cell stage blastomeres is random and cannot be predicted on a larger scale. One study in particular states that the position of the nucleus in each blastomere can be used to indicate how the cell will divide: if the nucleus is in the apical region then the cell will likely divide symmetrically, while if the nucleus is located in the basal region then the cell will likely divide asymmetrically.
193:; that is, blastomeres are capable of developing from a single cell into a fully fertile adult organism. This has been demonstrated through studies and conjectures made with mouse blastomeres, which have been accepted as true for most mammalian blastomeres as well. Studies have analyzed monozygotic twin mouse blastomeres in their two-cell state, and have found that when one of the twin blastomeres is destroyed, a fully fertile adult mouse can still develop. Thus, it can be assumed that since one of the twin cells was totipotent, the destroyed one originally was as well.
296:, can lead to the failure of cell cleavage and mitosis. When these necessary early cell divisions do not occur, the embryo can begin to form polyploid giant cancer cells that function very similarly to blastomere cells in order to grow and evolve in response to mechanical and chemical signals just like blastocyst precursors do. Studies have shown that these giant cancer cells are often also the genetic equivalent to somatic blastomeres.
260:. The first conjecture is known as the "inside-outside model", and states that the cells differentiate based on their state in the 16-cell stage or later. This means that, under this model, blastomere cells do not differentiate based on cellular differences, but rather they do so because of mechanical and chemical stimuli based on where they are positioned at that time.
197:
blastomeres in the cellular mass is not even, then the division should be asynchronous such that the sizes of the cells best support the mass's specific stage of differentiation. Blastomere size is typically considered uneven when one blastomere has a diameter over 25% larger than that of the other being compared.
263:
The other, more widely accepted model is known as the "cell-polarity model". This model states that the orientation of the cleavage plane at the 8-cell and 16-cell stages determines their later differentiation. There are two main ways in which blastomeres typically divide: symmetrically, meaning
196:
Relative blastomere size within the embryo is dependent not only on the stage of the cleavage, but also on the regularity of the cleavage amongst the cells. If the number of blastomeres in the cellular mass is even, then the sizes of the cells should be congruent. However, if the number of
304:
Oftentimes, clinicians and researchers will use blastomere biopsies in at-risk pregnant women as a way to test for genetic disorders. These biopsies are invasive, however, and have a major disadvantage when compared to other forms of invasive
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to not be divided evenly. Normally, when a cell divides each daughter cell has the same genetic material as the parent cell; if the genetic material does not split evenly between the two daughter cells, an event called
281:" occurs. Since this event occurs in only one of the several cells that exist at this point, the embryo will continue to develop but will have some normal cells and some abnormal cells. This disorder is called "
853:
Hastings RJ, Cavani S, et al. Cytogenetic
Guidelines and Quality Assurance: a common European framework for quality assessment for constitutional and acquired cytogenetic investigations. Eur J Hum Genet. 2007
244:, while the apolar cells will move to an inner position and begin developing into the embryo. The cells will then fully commit to their individual states in one of these two domains at the 32-cell stage.
512:
Li, Chao-Bo; Wang, Zhen-Dong; Zheng, Zhong; Hu, Li-Li; Zhong, Shu-Qi; Lei, Lei (2010-08-25). "Number of blastomeres and distribution of microvilli in cloned mouse embryos during compaction".
762:
Pickering, Susan J.; Johnson, Martin H.; Braude, Peter R.; Houliston, Evelyn (November 1988). "Cytoskeletal organization in fresh, aged and spontaneously activated human oocytes".
78:
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divides into two cells. The two-cell blastomere state, present after the zygote first divides, is considered the earliest mitotic product of the fertilized
66:
170:
does not increase, so each division results in smaller and smaller cells. When the zygote contains 16 to 32 blastomeres it is referred to as a
1029:
272:
It is possible for errors to occur during this process of repetitive cell division. Common among these errors is for the
921:
Gianaroli, Luca; Ferraretti, Anna P.; Crippa, Andor; Valerio, Marzia; Cafueri, Giulia; Pomante, Alessandra (March 2016).
205:
The division of blastomeres from the zygote allows a single fertile cell to continue to cleave and differentiate until a
178:
within the morula's cytosolic material in the blastomere cells can develop into important membrane functions, such as
252:
There are two main models for differentiation that determine which blastomere cells will divide into either the
1346:
617:
TARKOWSKI, ANDRZEJ K. (October 1959). "Experiments on the
Development of Isolated Blastomeres of Mouse Eggs".
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807:"The basal position of nuclei is one pre-requisite for asymmetric cell divisions in the early mouse embryo"
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in that only a few number of cells can be extracted at a time. Over time many specialists have switched to
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continue and result in a grouping of cells called blastomeres. During this process, the total size of the
1314:
1259:
1038:
923:"Preimplantation genetic testing: polar bodies, blastomeres, trophectoderm cells, or blastocoelic fluid?"
866:"Dedifferentiation into blastomere-like cancer stem cells via formation of polyploid giant cancer cells"
359:
Casser, E.; Israel, S.; Witten, A.; Schulte, K.; Schlatt, S.; Nordhoff, V.; Boiani, M. (December 2017).
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229:. These precursors typically appear when the blastomere differentiates into the 8- and 16-cell masses.
61:
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676:
Johnson, M (April 1981). "The foundation of two distinct cell lineages within the mouse morula".
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Johnson, M (April 1981). "The foundation of two distinct cell lineages within the mouse morula".
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317:, but blastomere biopsies can still be used for earlier-stage studies and genetic diagnostics.
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361:"Totipotency segregates between the sister blastomeres of two-cell stage mouse embryos"
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174:. These are the preliminary stages in the embryo beginning to form. Once this begins,
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of the blastomere allows for the development of two distinct cell populations: the
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Spindle, Akiko (1982-02-20). "Cell allocation in preimplantation mouse chimeras".
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Ajduk, Anna; Biswas
Shivhare, Sourima; Zernicka-Goetz, Magdalena (August 2014).
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452:"Production of monozygotic twins by splitting of 2-cell stage embryos in mice"
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TOGASHI, Mamoru; SUZUKI, Hiroshi; MIYAI, Tatsuya; OKAMOTO, Michio T (1987).
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Singh, Vishram. Textbook of
Clinical Embryology, 2nd Updated Edition.
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During the 8-cell differentiation period, the blastomeres form
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The
Developing Human: Clinically Oriented Embryology, 8th ed.
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182:. These pumps allow the inside of the embryo to fill with
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980:Moore, Keith L., Torchia, Mark G., and T. Persaud.
863:
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186:fluid, which supports the further growth of life.
1338:
987:Sermon, Karen, and Viville, Stéphane, editors.
864:Niu, N; Mercado-Uribe, I; Liu, J (2017-04-24).
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994:Bradshaw, Ralph, and Stahl, Philip, editors.
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154:. About 90 minutes after fertilization, the
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456:The Japanese Journal of Animal Reproduction
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1016:
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989:Textbook of Human Reproductive Genetics.
150:and continues through the first week of
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146:formation begins immediately following
122:; blastomeres are an essential part of
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975:Stedman's Medical Dictionary, 28th ed.
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776:10.1093/oxfordjournals.humrep.a136828
225:, which becomes the precursor to the
217:, which becomes the precursor to the
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507:
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425:"Cleavage and Blastocyst Formation"
13:
14:
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313:, which provide a lower level of
940:10.1016/j.fertnstert.2015.11.018
138:Human blastomere characteristics
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721:Journal of Experimental Zoology
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339:Encyclopædia Britannica Online
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288:This mosaicism, especially of
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189:The blastomere is considered
996:Encyclopedia of Cell Biology
690:10.1016/0092-8674(81)90502-X
580:10.1016/0092-8674(81)90502-x
240:and show precursors for the
7:
1315:Splanchnopleuric mesenchyme
1260:Splanchnopleuric mesenchyme
1039:Human embryonic development
823:10.1016/j.ydbio.2014.05.009
10:
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385:10.1038/s41598-017-08266-6
201:Blastomere differentiation
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526:10.1017/s0967199410000377
488:Atlas of Human Embryology
429:Colorado State University
248:Models of differentiation
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1320:Somatopleuric mesenchyme
1232:Somatopleuric mesenchyme
1041:in the first three weeks
927:Fertility and Sterility
1204:Regional specification
733:10.1002/jez.1402190311
86:Anatomical terminology
1347:Developmental biology
1310:Intraembryonic coelom
811:Developmental Biology
469:10.1262/jrd1977.33.51
152:embryonic development
484:"C. Blastomere size"
882:10.1038/onc.2017.72
631:1959Natur.184.1286T
625:(4695): 1286–1287.
377:2017NatSR...7.8299C
311:blastocyst biopsies
283:numerical mosaicism
764:Human Reproduction
365:Scientific Reports
114:(cleavage) of the
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1059:Oocyte activation
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268:Related disorders
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1197:Gastrulation
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492:. Retrieved
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433:. Retrieved
431:. March 2000
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342:. Retrieved
338:
335:"Blastomere"
329:
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195:
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184:blastocoelic
180:sodium pumps
176:microtubules
143:
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110:produced by
103:
101:
42:
16:Type of cell
1237:Neurulation
1162:Archenteron
1154:Germ layers
1104:Trophoblast
371:(1): 8299.
300:Diagnostics
209:forms. The
142:In humans,
43:blastomerus
32:Identifiers
1352:Embryology
1341:Categories
1293:Somitomere
1180:Blastopore
1144:Trilaminar
1094:Blastocyst
1089:Blastocoel
1084:Cavitation
1074:Blastomere
321:References
294:polyploidy
238:blastocyst
221:, and the
207:blastocyst
191:totipotent
144:blastomere
128:blastocyst
104:blastomere
22:Blastomere
1126:Hypoblast
1117:Bilaminar
949:0015-0282
890:0950-9232
784:1460-2350
741:0022-104X
647:0028-0836
588:0092-8674
534:0967-1994
393:2045-2322
315:mosaicism
162:. These
1283:Paraxial
1270:Mesoderm
1252:Endoderm
1214:Ectoderm
1192:Gastrula
1131:Epiblast
1069:Cleavage
957:26658131
908:28436947
870:Oncogene
841:24855000
706:22263112
655:13836947
604:22263112
550:23902185
542:20735894
411:28811525
290:diploidy
227:placenta
124:blastula
1140:Week 3
1113:Week 2
1003:(2020).
998:(2015).
991:(2014).
984:(2008).
977:(2006).
968:Sources
899:5582213
832:4111899
792:3204153
749:7061978
698:7237545
663:4148223
627:Bibcode
596:7237545
494:May 21,
435:May 21,
402:5557898
373:Bibcode
344:May 21,
256:or the
132:mammals
55:D001757
27:Details
1288:Somite
1079:Morula
1064:Zygote
1047:Week 1
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619:Nature
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514:Zygote
490:. 2016
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219:embryo
172:morula
168:embryo
160:oocyte
156:zygote
118:after
116:zygote
702:S2CID
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