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Determination of Reproductive Competence by Confirming Pubertal Onset and Performing a Fertility Assay in Mice and Rats
Published on: October 13, 2018
Do histocompatibility genes influence sex ratio (% males)?
1Jackson Laboratory, Bar Harbor, Maine 04609.
Reproduction, Fertility, and Development
|January 1, 1991
Summary
A specific mouse strain (B10.R111) exhibited a higher male offspring ratio, linked to a diet-gene interaction causing female mortality. This highlights variability in secondary sex ratios.
Area of Science:
- Genetics and Developmental Biology
- Animal Reproduction and Sex Ratios
Background:
- The Special Mouse Stocks Resource (SMSR) observed a higher proportion of male offspring in some C57BL/10SnJ Congenic Histocompatibility Mouse Strains.
- Strain B10.R111(71NS) (R) showed a significantly higher male proportion (55.68%) compared to the progenitor strain C57BL/10SnJ (B) (49.81%).
Purpose of the Study:
- To investigate the cause of the skewed sex ratio in specific mouse strains within the SMSR.
- To determine if dietary factors or genetic background influenced the observed sex ratio bias.
Main Methods:
- Comparison of breeding records from SMSR colonies with mice fed Old Guildford diets.
- Breeding of B and R strains at Jackson Laboratory on Wayne Sterilizable Rodent Blox.
- Examination of over 5000 inbred, hybrid, and backcross fetuses and neonates for sex ratio analysis.
Main Results:
- No male excess was found in fetuses examined at Jackson Laboratory, suggesting a primary sex ratio near 50%.
- Neonatal sex ratios were slightly skewed towards males, indicating perinatal female loss.
- The R strain's high sex ratio was attributed to a potential interaction between its H-2 haplotype and the Old Guildford diet, negatively impacting female survival.
Conclusions:
- The study suggests that female perinatal loss, influenced by a gene-diet interaction, is responsible for the skewed sex ratio in the R mouse strain.
- The findings underscore the significant variability in secondary sex ratios and caution against using the R strain as a model for human male bias.
- Dietary components and genetic background are critical factors influencing mammalian sex ratios during development and perinatal periods.
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