CHAPTER 7 - GENETIC METHODS
Suggested Guidelines for Maintaining Mutant stocks
(Source: M. Halpern)
Densities
With adequate water flow, stocks are routinely kept at densities of:
- 1 fish per 1/4 gallon `tanklet'
- 25 fish per 5 gallon tank
- 50 fish per 10 gallon tank
- 150 fish per 30 gallon tank
Intercrosses
To obtain maximal numbers of identified heterozygotes, keep mutant working stocks as intercrosses from identified heterozygous parents. The wild-type progeny from several intercrosses should be pooled to maximize the genetic diversity of the stock. Use identified fish from one generation for experiments, while another generation of intercross progeny are growing towards sexual maturity. On average, make a new generation every 4-6 months.
+/m X +/m
+/+ +/m m/m
1/3 2/3 (die)
Outcrosses
To maintain a mutant line, heterozygous fish should also be outcrossed to the wild-type main line. Ideally, the outcross stock should also be derived from group matings rather than a single cross. Identified heterozygous males can be used for freezing sperm.
+/m X +/+
+/m +/+
1/2 1/2
Tank usage
Depending on the use of a given stock, estimate the number of tanks required for stock maintenance, mutant recovery, and experimental purposes:
Category 1: Working stock for maintenance and low level usage
3 X 5 gallon:
- 2 for identified heterozygotes
- 1 for wild-type outcross
4 X 10 gallon:
- 2 to identify heterozygotes
- 2 for growing fish to sexual maturity
Category 2: Recovering mutations from clonal fish
- F1: 1 tanklet for original female
- 1 X 10 gallon for first outcross (approximately 50 fish)
- F2: 4 tanklets to hold fish being identified
- 2 X 5 gallon initially for intercrosses
Category 3: Major working line
Tanks are needed for
- intercrosses
- wild-type outcross
- double mutant stocks
- special backgrounds (i.e. golb1 for line-age or nicb1 for physiology)
- extra females for squeezing purposes
- identified single and double mutant heterozygotes
This means at least: 10 X 5 gallon, 5 X 10 gallon and 2 X 30 gallon.
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