These ES cells are heterozygous for the knockout mutation. Although these cells will grow and divide in culture, they cannot form an embryo that will develop into a mouse on their own. Step 4 ...

This was more evident in mature mice, with heterozygous mice showing an intermediate phenotype (Fig. 3e). The presence of these hemorrhagic structures may result from the normal process of ...

Hemann et al. crossbred telomerase-deficient mice having short telomeres with mice heterozygous for telomerase activity that have long telomeres. They found that the phenotype of the telomerase null ...