A homozygous null mutant mouse for the gene xyz exhibits embryonic lethality by early gestation. Chimeric mice composed of xyz null cells and wild-type cells survive to adulthood and display abnormal limb development, characterized by the formation of extra digits. Closer examination of the extra digits reveals that xyz null cells are concentrated in these regions.
Which of the following inferences can correctly be drawn from this experiment?
1
Wild-type xyz function in developing limbs induces digit specification in neighboring cells
2
Wild-type xyz function in developing limbs suppresses digit specification in neighboring cells.
3
xyz function is completely cell autonomous.
4
xyz function is limb-specific.