ESC mice produced by tetraploid complementation using both type <i>a</i> and type <i>b</i> 4n blastocysts.

<p>(A) Newborn pups obtained using type <i>a</i> and type <i>b</i> 4n blastocysts by tetraploid complementation. Pups from type <i>b</i> 4n blastocysts are frequently displaying abdominal hernia (arrow indicated), while pups from type <i>a</i> 4n blastocyst are all normal. (B) A litter of ESC pups (white coat color) produced using type <i>a</i> 4n blastocysts (black coat color); one pup (arrow indicated) displayed substantial contribution of cells from the host 4n embryo (over 20% of contribution from the host embryo judging by the coat color). (C) The efficiency to obtain ESC mice from type <i>a</i> or type <i>b</i> 4n blastocysts is not significantly different (<i>χ²</i>-test, <i>P</i> = 0.13). (D)The frequency of herniated pups using type <i>b</i> blastocysts is significantly higher than using type <i>a</i> blastocysts (<i>χ²</i>-test, <i>P</i><0.01). (E) A model for tetraploid complementation illustrates ESC mice from type <i>a</i> 4n blastocysts are possibly 2n/4n chimeras, whereas ESC mice from type <i>b</i> 4n blastocysts could be pure ESC-derived.