Lin28b plays a role in the regulation of stem cell maturation and hematopoietic stem cell self-renewal, indicating its involvement in stress erythropoiesis. To determine the function of Lin28b, Lin28b knockout mice will be produced using CRISPER-Cas9 RNA-guided DNA endonucleases. The sequence will be cloned through a culture of mouse stem cells, and altered cells will be inserted with the mouse blastocyst to produce Lin28b -/- offspring, which will be observed to determine the gene’s function.