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Doctors Report World’s Second Case of “Semi-Identical” Twins
Doctors Report World’s Second Case of “Semi-Identical” Twins
The extremely rare event, thought to be caused by two sperm cells fertilizing the same egg simultaneously, was last reported in 2007.
Doctors Report World’s Second Case of “Semi-Identical” Twins
Doctors Report World’s Second Case of “Semi-Identical” Twins

The extremely rare event, thought to be caused by two sperm cells fertilizing the same egg simultaneously, was last reported in 2007.

The extremely rare event, thought to be caused by two sperm cells fertilizing the same egg simultaneously, was last reported in 2007.

developmental biology, cell & molecular biology

amphibian hindlimb chicken animal feet hand development reactive oxygen species fingers digits webbing webbed
Image of the Day: Phantom Limbs
Chia-Yi Hou | Jun 17, 2019 | 1 min read
Researchers study how oxygen around an embryo helps shape the way feet and digits form in amphibians and chickens.
Prenatal Exposure to Cannabis Affects the Developing Brain
Andrew Scheyer | Jan 1, 2019 | 10+ min read
Children born to moms who smoked or ingested marijuana during pregnancy suffer higher rates of depression, hyperactivity, and inattention.
Fastest-Ever Cell Contractions Observed in Primitive Invertebrate
Abby Olena, PhD | Dec 13, 2018 | 4 min read
The microscopic marine animal Trichoplax adhaerens may use rapid changes in cell shape to avoid being ripped apart by forces in the ocean.
Discovery’s Crest: A Profile of Marianne Bronner
Anna Azvolinsky | Dec 1, 2018 | 8 min read
Studying how neural crest cells journey through the embryo, this Caltech developmental biologist has revealed how they form major cell types, including peripheral neurons, bone, and smooth muscle.
Mouse Stem Cells Made to Form Embryo-Like Structures
Ruth Williams | Oct 3, 2018 | 3 min read
With just a molecular nudge, aggregates of embryonic stem cells take shape as a “gastroloid,” bearing the genetic hallmarks and spatial organization of early development.
Image of the Day: Transgenic Axolotl
Kerry Grens | Oct 3, 2018 | 1 min read
Lineage tracing reveals how cells help the salamanders regrow chopped-off limbs.
Adult Cardiac Stem Cells Don’t Exist: Study
Diana Kwon | Sep 5, 2018 | 3 min read
A mouse study adds to the growing body of work disputing the ability of progenitor cells to regenerate muscle tissue in adult mammals’ hearts.
These Molecules Zipper Embryos Closed
Ashley Yeager | Aug 1, 2018 | 2 min read
Actin rings seal off the ball of cells, aiding in implantation in the uterus. But faults in the process could explain why some pregnancies fail.
Artificial Mouse Embryo Made in a Laboratory
Sukanya Charuchandra | Jul 25, 2018 | 1 min read
The embryo, grown in a dish from several types of stem cells, went through gastrulation, a significant stage in development.
Pancreatic Cell Size Negatively Relates to Lifespan in Mammals
Sukanya Charuchandra | Jun 19, 2018 | 2 min read
Species with larger pancreatic cells tend to have shorter lives, according to a study.  
Animals’ Embryonic Organizer Now Discovered in Human Cells
Jim Daley | May 23, 2018 | 4 min read
The finding confirms that a cluster of cells that directs the fate of other cells in the developing embryo is evolutionarily conserved across the animal kingdom.
Infographic: Skotomorphogenesis Versus Photomorphogenesis
Kerry Grens | Jan 31, 2018 | 1 min read
Pectin fragments may signal plant cells to maintain a type of growth suited to darkness.
Captivated by Chromosomes
Anna Azvolinsky | Dec 1, 2017 | 8 min read
Peering through a microscope since age 14, Joseph Gall, now 89, still sees wonder at the other end.
New Techniques Detail Embryos’ First Hours and Days
Jef Akst | Dec 1, 2017 | 10+ min read
New technologies reveal the dynamic changes in mouse and human embryos during the first week after fertilization.
Macrophages Are the Ultimate Multitaskers
Claire Asher | Oct 1, 2017 | 10+ min read
From guiding branching neurons in the developing brain to maintaining a healthy heartbeat, there seems to be no job that the immune cells can’t tackle.
Infographic: Macrophages Around the Body
Claire Asher | Sep 30, 2017 | 2 min read
In addition to circulating in the blood as immune sentinels, macrophages play specialized roles in different organs around the body.
Famed Mammalian Embryologist Dies
Jef Akst | Dec 1, 2016 | 2 min read
Andrzej Tarkowski’s research laid the groundwork for future advances in cloning, stem cell research, and in vitro fertilization.
Editing Genomes to Record Cellular Histories
Ruth Williams | May 26, 2016 | 3 min read
Researchers harness the power of genome editing to track cell lineages throughout zebrafish development.
Embryo Watch
Jef Akst | May 5, 2016 | 2 min read
A new culture system allows researchers to track the development of human embryos in vitro for nearly two weeks.
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