Genetic mapping of the bd locus

Michael T. Lewis and Jerry F. Feldman - Department of Biology, 337 Sinsheimer Labs, University of California, Santa Cruz, CA 95064.

As an initial step toward cloning the band (bd) gene, we sought to pinpoint its genetic location relative to known flanking markers on LGIV prior to initiating a chromosome walk.

Previous data (Table 1) from Sargent & Woodward (1969 J. Bacteriol. 97:861-866) showed the bd gene distal to pan-1 by 1.5 map units. Our follow-up crosses (Table I) show bd to be far more distal than anticipated. By two and three point crosses, we now place bd 8.9 map units distal to met-5 and 18.8 map units proximal to nit-3. The gene order is therefore:

centromere/trp-4/pan-1/cot-1/his-4/met-5/bd/nit-3

Table 1. Results of genetic crosses

Zygote genotype and recombinaton percentage Parentals Singles

Region 1

 Singles

Region 2

 Doubles Total
+ 8.5 + 1.5 bd

trp-4 pan-1 +

87

92

 11

6

 2

1

 0

0

 199a
pan-1 4.0 + 12.1 +

+ cot-1 bd

59

68

 3

1

 5

11

 1

1

 149
cot-1 3.7 his-4 18.3 +

+ + bd

52

99

 1

4

 11

22

 1

1

 191
cot-1 4.1 + 8.9 bd

+ met-5 +

67

60

 6

0

 10

3

 0

0

 138
cot-1 16.6 bd 18.8 +

+ + nit-3

63

90

 12

21

 33

5

 2

3

 229

a From Sargent and Woodward (1969) J. Bact. 97:861-866.

These data, once again, highlight the variability sometimes observed in Neurospora genetic crosses as well as the importance of establishing flanking genetic markers prior to initiating a chromosome walk.

Acknowledgements

We wish to thank Mignon Fogarty and Katie Wymore for technical assistance.