Worm Breeder's Gazette 10(2): 93
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
contigs=
515
mean contig size=
141kb
Linkage of the existing cosmid contigs by means of yeast artificial
chromosomes (YACs) is proceeding steadily. Two grids have been
prepared: one of 2700 YACs, the other of 2000 representative lorist
cosmids. Since the YAC and lorist vectors do not cross-hybridize, we
are able to probe back and forth between the two grids. The
proportion of the genome in identified contigs has advanced to 40%,
and is depicted (in a somewhat imaginative fashion) on the chromosomal
contig maps below.
In light of some recent comments, we want to emphasize two points
about the mapping of newly cloned genes. First, the optimal mapping
strategy is still to send your clone to the MRC, regardless of whether
or not you are probing YAC filters with it. Provided the clone falls
into a mapped region, fingerprinting provides a secure assignment,
regardless of dispersed repeat sequences, and also positions the clone
more accurately than is possible by hybridization alone. Second,
although the existence and position of your clone become public, the
clone itself (and any contiguous clones) do not. Enquiries about the
region immediately adjacent to your clone are invariably directed back
to you before we send out any material.
CHROMOSOMAL CONTIG
MAPS
The genome map data has become sufficiently extensive and complex
that a pictorial overview may now be useful. The accompanying maps
are a first attempt; they are an optimized computation based on all
the data - genetic, in situ, and contig - that we have at present.
Horizontal lines delineate those contigs that have been positioned on
the chromosomes to date. The long range ordering, down to 15-20%, is
likely to be secure; the short range ordering, except for that defined
by markers on the line of the genetic map, is arbitrary. Nevertheless,
the maps should give a reasonably accurate impression of the regions
of the genome that have been covered so far. Other regions are, of
course, likely to be covered also, but we have no means of knowing
until new markers or further linkage reveal them. Please ask us for
more information about areas that particularly interest you, and tell
us about any features of the map with which you disagree. Please also
give us official names for all those upper case (i.e. temporary)
genetic markers.
For practical reasons, we have chosen to plot the data on a metric
defined by in situ hybridization, rather than on a genetic metric (in
which the clusters are highly compressed, because of suppression of
recombination - see CSH meeting abstracts, 1988, p12). However, it is
interesting that even on this physical metric there is a lot of
unassigned space in the arms. J. S. bets R. W. that there really is
plenty of gene-poor DNA out there; R. W. bets J. S. that it's some
kind of artefact. We shall see.
{maps excluded due to poor
reproducibility}