= Replica plating
{wiki}
<Replica plating> transfers samples from corresponding <biological colonies> or patches to several growth conditions while preserving their spatial arrangement. A master plate makes it possible to relate growth or failure at one location to the same source population on another plate.
The master preserves the source <biological colonies>; each replica tests a sample of their <biological cells>. A fabric carrier takes one spatial impression from the master and deposits samples onto fresh plates. Different <cell culture medium> formulations can then reveal different growth <phenotypes> at corresponding sites. The carrier copies locations, not a guaranteed number of <biological cells>. <Replica plating spatial correspondence> therefore lets an investigator connect a readout to a recoverable source without treating every empty replica site as a missing master <biological colony>.
\Image[/replica-plating-velveteen-spatial-transfer.png]
{title=<Replica plating>: a fabric carrier copies locations while the master preserves the source}
{description=Original apparatus and transfer schematic with invented <biological colony> positions. The left panel separates the inverted plate, fabric pile, retaining hoop and support for clarity. The right panel shows aligned plate views after incubation; the fabric holds an imprint rather than growing the pictured <biological colonies>. Arrows show sample transfer. The dotted return arrow shows using a location to recover material from the unexposed master, not transferring material back from a challenged replica. Sizes and growth outcomes are schematic.}
The useful trick is that a destructive or growth-restricting test can interrogate one sample while another remains available. In <indirect selection of bacterial mutants>, the replica supplies information about which source to recover. This also makes a failure-to-grow <phenotype> accessible: a missing replica <biological colony> cannot be picked, but its source may still be present on the master. Matching positions is the bridge between testing and retrieval.
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