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Published on: July 11, 2019
Accumulation of lethals in highly selected lines of Drosophila melanogaster
A García-Dorado1, C López-Fanjul
1Departamento de Genética, Facultad de Biología, Universidad Complutense de Madrid, 3, Madrid, Spain.
Abstract:
Four synthetic lines of D. melanogaster selected for low sternopleural bristle number for 50 generations were screened for lethals on chromosome III when their mean score equalled 2.5. Each line originated from a cross between line M (previously selected for the same trait during 130 generations) and a different unselected cage population. Line M was already known to carry a recessive lethal on chromosome III affecting the selected trait, such that the bristle score of the lethal heterozygote was lower than that of the viable homozygote. Tests revealed 18 lethals, 15 of these present in at least two lines. Each line carried from 10 to 16 lethals. All lines carried groups of lethals present on the same chromosome, and at least six lethals in each line were included in such an association with a frequency of 0.18 or higher. It appears that the lethal affecting bristle score in line M has protected a segment of chromosome III from natural selection and that the remaining 14 lethals have accumulated later in that line.
Insights
Genetic selection in Drosophila melanogaster revealed accumulated lethals on chromosome III. A pre-existing lethal in line M protected linked genes, allowing further lethal mutations to accumulate.
Area of Science:
- Evolutionary genetics
- Developmental biology
Background:
- Artificial selection can uncover genetic variation and mutations.
- Drosophila melanogaster is a model organism for genetic studies.
- Recessive lethals can impact quantitative traits.
Purpose of the Study:
- To screen for recessive lethals on chromosome III in Drosophila melanogaster lines selected for low sternopleural bristle number.
- To investigate the impact of a known lethal in line M on the accumulation of other lethals.
Main Methods:
- Four synthetic lines of Drosophila melanogaster were created by crossing line M with unselected populations.
- Lines were selected for low sternopleural bristle number for 50 generations.
- Lethals on chromosome III were screened when the mean bristle score reached 2.5.
Main Results:
- Eighteen recessive lethals were identified on chromosome III.
- Fifteen lethals were present in at least two of the four lines.
- Each line carried 10–16 lethals, often grouped on the same chromosome.
- A significant association between lethals and a frequency of 0.18 or higher was observed.
Conclusions:
- A recessive lethal in line M appears to have protected a linked chromosomal segment from natural selection.
- This protection facilitated the accumulation of additional recessive lethals on chromosome III.
- The findings shed light on the dynamics of mutation accumulation under relaxed selection.
