Watanabe T K, Yamaguchi O, Mukai T
Genetics. 1976 Jan;82(1):63-82. doi: 10.1093/genetics/82.1.63.
Five hundred and two third chromosomes were extracted from a large cage population of Drosophila melanogaster initiated two months after collection of the progenitors near Raleigh, North Carolina in 1970.---Salivary gland chromosomes of 489 chromosome lines were examined and 54 chromosomes were found to carry inversions. The inversions were classified into three polymorphic types [In (3L)P, In (3R)P, and In (3R)C] and two unique types. The polymorphic inversions were found in frequencies of 0.012, 0.88, and 0.010, respectively.--Viabilities of homozygotes and heterozygotes were examined. Chromosomes with lethals occurred with a frequency of 0.495: 0.537 in the group of inversion-carrying chromosomes and 0.490 in the group of inversion-free chromosomes. The average homozygote viability computed on the basis of an average heterozygote viability of 1.0000 was 0.3235 if lethal lines were included and 0.6290 if they were excluded. The detrimental load to lethal load ratio (D:L ratio) was 0.70 (=0.4636-0.6650). The average viability of lethal heterozygotes was significantly larger than that of lethal-free heterozygotes. It appears, however, that lethal genes in heterozygotes have deleterious effects on fitness as a whole.--The average degree of dominance for viability polygenes was estimated to be about 0.3-0.4 in lethal-free individuals and nearly zero in lethal heterozygotes. Overdominance or some form of balancing selection was suggested at some loci. The difference between the values obtained for average degree of dominance due to genetic backgrounds and superior vibaility of lethal heterozygotes (but not fitness as a whole) suggest that some epistasis or coadaptation occurs.--The results described above are similar to those obtained for the second chromosomes.
1970年在北卡罗来纳州罗利附近采集果蝇祖先两个月后，从一个大型果蝇笼养群体中提取了502条三分之二的染色体。——检查了489个染色体系的唾液腺染色体，发现有54条染色体带有倒位。这些倒位被分为三种多态类型[In(3L)P、In(3R)P和In(3R)C]和两种独特类型。多态倒位的频率分别为0.012、0.88和0.010。——检查了纯合子和杂合子的活力。携带致死基因的染色体在携带倒位染色体组中的出现频率为0.495:0.537，在无倒位染色体组中的出现频率为0.490。如果包括致死系，基于平均杂合子活力为1.0000计算的平均纯合子活力为0.3235；如果排除致死系，则为0.6290。有害负荷与致死负荷之比（D:L比）为0.70（=0.4636 - 0.6650）。致死杂合子的平均活力显著高于无致死杂合子。然而，杂合子中的致死基因似乎对整体适应性有有害影响。——在无致死个体中，活力多基因的平均显性程度估计约为0.3 - 0.4，在致死杂合子中几乎为零。在某些位点存在超显性或某种形式的平衡选择。由于遗传背景和致死杂合子的较高活力（但不是整体适应性）而获得的平均显性程度值之间的差异表明发生了一些上位性或共适应。——上述结果与第二条染色体的结果相似。
