Passage
Neurulation refers to the early formation of the nervous system in vertebrate embryos and begins when the notochord, a rodlike mesodermal structure, induces neural tube and neural crest cell formation in the ectoderm. Neural tube defects (NTDs) arise from abnormalities in the development of the neural tube and can range from mild to severe, depending on which portion of the tube is affected. Spina bifida, a form of NTD, is divided into three categories. The most serious subclassification of spina bifida is myelomeningocele, which occurs when the lower spine fails to close, which leaves the spinal cord and nerve roots in the lower back damaged and exposed.NTDs are thought to be caused in part by folate deficiency. Folate plays a critical role in normal cell division and growth as it is a necessary coenzyme for DNA synthesis and methylation. Mutations in several genes involved in folate metabolism have been associated with an increased risk for NTDs. It has been hypothesized that folate decreases NTD risk by ameliorating oxidative stress, thereby reducing damage to developing cells in the embryo. Certain maternal conditions, such as high blood glucose, increase the risk of NTD development by enhancing embryonic oxidative stress during crucial developmental periods.A study was conducted to examine how supplementation with folic acid, the dietary form of folate, affected pregnant women who were identified to have preexisting diabetes, pregestational obesity (another risk factor for NTD), or no preexisting conditions (control group). Higher folic acid intake decreased the incidence of embryonic NTDs among pregnant women with diabetes, but no significant effect was found for pregnant women who were obese.
Adapted from Parker SE, Yazdy MM, Tinker SC, Mitchell AA, Werler MM. The impact of folic acid intake on the association among diabetes mellitus, obesity, and spina bifida. Am J Obstet Gynecol. 2013;209(3):239.e1-8.
-Undifferentiated gastrula cells presumed to give rise to neural tissue were transplanted from a donor frog embryo onto an undifferentiated gastrula area of a host frog embryo. The transplantation region in the host was presumed to give rise to epidermal tissue. Both host and donor embryos were allowed to develop following the transplant, and gave rise to two normal embryos. What was the purpose of this experiment?

Question

Passage
Neurulation refers to the early formation of the nervous system in vertebrate embryos and begins when the notochord, a rodlike mesodermal structure, induces neural tube and neural crest cell formation in the ectoderm.  Neural tube defects (NTDs) arise from abnormalities in the development of the neural tube and can range from mild to severe, depending on which portion of the tube is affected.  Spina bifida, a form of NTD, is divided into three categories.  The most serious subclassification of spina bifida is myelomeningocele, which occurs when the lower spine fails to close, which leaves the spinal cord and nerve roots in the lower back damaged and exposed.NTDs are thought to be caused in part by folate deficiency.  Folate plays a critical role in normal cell division and growth as it is a necessary coenzyme for DNA synthesis and methylation.  Mutations in several genes involved in folate metabolism have been associated with an increased risk for NTDs.  It has been hypothesized that folate decreases NTD risk by ameliorating oxidative stress, thereby reducing damage to developing cells in the embryo.  Certain maternal conditions, such as high blood glucose, increase the risk of NTD development by enhancing embryonic oxidative stress during crucial developmental periods.A study was conducted to examine how supplementation with folic acid, the dietary form of folate, affected pregnant women who were identified to have preexisting diabetes, pregestational obesity (another risk factor for NTD), or no preexisting conditions (control group).  Higher folic acid intake decreased the incidence of embryonic NTDs among pregnant women with diabetes, but no significant effect was found for pregnant women who were obese.
Adapted from Parker SE, Yazdy MM, Tinker SC, Mitchell AA, Werler MM. The impact of folic acid intake on the association among diabetes mellitus, obesity, and spina bifida. Am J Obstet Gynecol. 2013;209(3):239.e1-8.
-Undifferentiated gastrula cells presumed to give rise to neural tissue were transplanted from a donor frog embryo onto an undifferentiated gastrula area of a host frog embryo.  The transplantation region in the host was presumed to give rise to epidermal tissue.  Both host and donor embryos were allowed to develop following the transplant, and gave rise to two normal embryos.  What was the purpose of this experiment?

Quizplus · Accepted Answer

11ecba2d_0fc1_dade_a3bf_2b067529f611_MD0008_00 Cell determination (specification of cell fate) and differentiation (acquisition of unique/specialized biochemical and structural cellular characteristics) in the embryo result from the asymmetric segregation of cytoplasmic determinants and from inductive signaling. In inductive signaling, an inducer (the signaling cell) releases chemical signals that act on competent neighboring cells (ie, those cells that express the appropriate receptors capable of responding to the signal) by regulating the expression of specific genes. This signaling provides the competent cells with positional and fate-determining information required for proper development. In the experiment described, the researchers removed undifferentiated gastrula cells that were presumed to give rise to neural tissue from one embryo (donor) and transplanted them onto a different gastrula (host) at a non-neural location. The researchers wanted to determine whether the prospective donor neural cells would continue to develop independently into nervous tissue or if they would assume a different tissue type or cell fate due to communication with surrounding cells. The transplanted donor cells developed into normal epidermal tissue in the host, suggesting that signals from the surrounding skin-destined cells influenced the fate of the transplanted cells. (Choice A) Based on the description of the experiment, researchers already knew which portion of the undifferentiated gastrula would likely give rise to epidermal tissue because they were able to transplant undifferentiated prospective neural tissue onto that area. (Choice C) The entire experiment was conducted after the blastula phase of embryogenesis; therefore, gaining insight about the developmental fates of cells in the blastula was not the purpose of this experiment. (Choice D) The question states that the researchers used undifferentiated cells, which are cells that have not yet acquired any observable changes characteristic of commitment. Undifferentiated cells cannot be used to determine whether or not differentiation can be reversed. To determine if differentiation can be reversed, the researchers would have to assess whether the acquired changes of differentiated cells would revert following transplantation. Educational objective: Cell fate is influenced by inductive signaling between cells in the early embryo. In inductive signaling, an inducer (the signaling cell) releases chemical signals that act on competent neighboring cells by regulating the expression of specific genes required for cell determination.

Passage Neurulation Refers to the Early Formation of the Nervous System