What do we call the first few divisions of the zygote? What process must occur to allow these divisions?
I would assume that it is called mitosis. However, since this is not my area of expertise, I searched Google under the key words "zygote divisions" to get these possible sources:
http://books.google.com/books?id=gtcfggF79wAC&pg=PA114&lpg=PA114&dq=zygote+divisions&source=web&ots=EuaM3Kefte&sig=auuRJneb8ZUK2VDTSPWz4eU3JCI&hl=en#PPA115,M1
http://www.visembryo.com/baby/2.html
http://en.wikipedia.org/wiki/Zygote
http://books.google.com/books?id=HhyBZfQsfGYC&pg=PA183&lpg=PA183&dq=zygote+divisions&source=web&ots=ARVnxL4eE2&sig=uShVHR-1dJKBIVHw3Ej8ZEmHBPo&hl=en#PPA185,M1
http://mansfield.osu.edu/~sabedon/campbl21.htm
In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.
I hope this helps. Thanks for asking.
The first few divisions of the zygote are called cleavage divisions. Cleavage refers to the series of mitotic cell divisions that occur in the early stages of embryonic development. During cleavage, the zygote divides into smaller cells called blastomeres.
To understand the process of cleavage divisions, it is important to know that they occur in animal embryos, specifically those that undergo holoblastic cleavage. Holoblastic cleavage is a type of cleavage that occurs when the entire zygote divides into separate blastomeres.
The process of cleavage is driven by the activation of the zygote's own genetic machinery, which leads to the division of the cytoplasm and the replication of DNA. This process occurs through a series of cell divisions without any significant growth of the embryo.
Initially, the zygote undergoes its first division, resulting in two daughter cells. These two cells then divide again, resulting in four cells, followed by further divisions to form eight cells, and so on. As each division occurs, the blastomeres become successively smaller due to the division of cytoplasmic contents into the increasing number of cells.
Cleavage divisions are essential for the establishment of the body plan and the differentiation of various cell lineages during embryonic development. These divisions also help in the distribution of essential macromolecules and organelles to individual blastomeres, ensuring that each cell receives the necessary components for further development.
In summary, the first few divisions of the zygote are called cleavage divisions, and they are responsible for the initial segmentation and cellularization of the early embryo.