  We study some stochastic models of physical mapping of genomic sequences. Our
starting point is a global construction of the process of the clones and of the
process of the anchors which are used to map the sequence. This yields explicit
formulas for the moments of the proportion occupied by the anchored clones,
even in inhomogeneous models. This also allows to compare, in this respect,
inhomogeneous models to homogeneous ones. Finally, for homogeneous models, we
provide nonasymptotic bounds of the variance and we prove functional invariance
results.
