A child is born prematurely and experiences severe asthma. Which most likely affected cell differentiation when the was a developing embryo?

The most likely factor that affected cell differentiation when the child was a developing embryo is a mutation in the GATA3 gene.

GATA3 is a transcription factor essential for the development of several organs and tissues, including the lungs. Mutations in the GATA3 gene can lead to various conditions, including congenital heart defects, immunodeficiency, and severe asthma.

In the case of the child born prematurely with severe asthma, a mutation in the GATA3 gene likely disrupted the normal development of the lungs. This could have led to the child being born with underdeveloped lungs, making them more susceptible to asthma and other respiratory problems.