The assembly of the individual BACs into entire chromosome arms was verified in two ways.

The sequence of chromosome arm 4 in Release 3 extends proximally to that of Release 2 by nearly 60 kb.

To generate quality scores for an entire chromosome arm, we associated a phrap consensus score with each base.

The chromosome arm is already copied during S phase of the cell cycle.

These data show that the large Release 3 sequence contigs extend into the centric heterochromatin on these five chromosome arms.

This may reflect more complete sequencing on 1p, or perhaps differing DNA-packing densities on the two chromosome arms.

These clusters could cover an entire chromosome arm.

Consistent with this is the fact that rearranged sequences can be inferred to come from the same chromosome arm.

Only part of the duplicated region may have been transposed to the other chromosome arm.

The remaining autosomal pairs are smaller and acrocentric (with the shorter chromosome arm difficult to observe).