TABLE 4

Counting “lethal equivalents” in inbred lines of the Pacific oyster

LineTally of highly deleterious mutationsaNo. of independent segregationsbMap length covered (cM)cEstimated no. of lethal genes per founder genomedConfidence limits (95%) on estimatee
Line 261647812.65.1–21.6
Line 31 (2)5 (6)132 (168)7.6 (11.9)0.2–21.3
Line 56 (7)21 (23)447 (511)13.4 (13.7)4.6–21.4
7 × 6 F151639812.64.4–23.6
  • a Tally of highly deleterious recessive mutations (s ≈ 1.0) implied by deficiencies of microsatellite IBD homozygotes. Numbers in parentheses for lines 3 and 5 include mutations implied by significant deficiencies of grandparental heterozygotes in F2 or F3 families.

  • b The number, over all descendant families and markers, of independent segregations producing an IBD homozygote for a grandparental allele. Numbers in parentheses include segregations producing deficiencies of grandparental heterozygotes.

  • c The sum of coverage provided by independent informative segregations, assuming that a recessive lethal mutation with 18 cM of a marker would produce a significant distortion of segregation ratio (see materials and methods); coverage is adjusted for linkage of markers.

  • d The per genome estimate of “lethal equivalents” multiplies the number of lethal genes per map unit by 1000 cM, an estimate of the total map length of the oyster genome.

  • e Confidence limits, calculated from the exact binominal cumulative probability distribution (see materials and methods), given n independent informative segregations (column 3) and k highly deleterious recessive mutations detected as deficiencies of IBD homozygotes (column 2).