Related Experiment Video
Updated: Feb 23, 2026
05:24
Determining the Egg Fertilization Rate of Bemisia tabaci Using a Cytogenetic Technique
Published on: April 1, 2019
5.8K
A father effect explains sex-ratio bias
Aurelio F Malo1,2,3, Felipe Martinez-Pastor4,5, Francisco Garcia-Gonzalez6,7
1Department of Zoology, University of Oxford, Oxford OX1 3PS, UK aurelio.malo@zoo.ox.ac.uk.
Proceedings. Biological Sciences
|September 1, 2017
Summary
Fathers can influence offspring sex ratio through sperm morphology. Differences in sperm nucleus area, linked to genetic variation, explain litter sex ratio variation and a higher proportion of sons.
Area of Science:
- Evolutionary biology
- Reproductive biology
- Genetics
Background:
- Parental investment theory predicts sex ratio adjustment when male and female offspring fitness returns vary.
- Paternal control over offspring sex ratio was historically dismissed due to expected equal proportions of X- and Y-chromosome-bearing sperm (CBS).
- Recent findings challenge the assumption of equal CBS proportions, opening avenues for investigating male-driven sex ratio bias.
Purpose of the Study:
- To demonstrate father-exclusive control over offspring sex ratio in *Peromyscus leucopus*.
- To identify the mechanism by which male-driven sex ratio bias is achieved.
- To explore the relationship between paternal genetic variation and sex ratio bias.
Main Methods:
- Utilized *Peromyscus leucopus* as a model organism.
- Identified a sperm morphological marker (sperm nucleus area) associated with sex ratio bias.
- Quantified the variation in litter sex ratio explained by differences in sperm nucleus area among males.
- Assessed the mediating role of sperm nucleus area in the relationship between paternal genetic variation and sex ratio bias.
Main Results:
- Differences in male sperm nucleus area explained 22% of the variation in litter sex ratio.
- Paternal genetic variation, measured by the inbreeding coefficient, was inversely related to sperm nucleus area.
- Fathers with higher genetic variation sired a higher proportion of sons (25% increase in sons per 0.1 decrease in inbreeding coefficient).
Conclusions:
- Paternal control over offspring sex ratio is a significant factor in vertebrates.
- Sperm nucleus area acts as a mediator linking paternal genetic variation to sex ratio bias.
- These findings provide a mechanism for male-driven sex ratio biases and have implications for understanding sex allocation strategies and human sex ratio variations.
Related Concept Videos
02:45The Ratio of X Chromosome to Autosomes
9.9K
In most organisms, sex is determined by the ratio of X and Y chromosomes. However, in some organisms, such as Drosophila and C.elegans, sex is determined by the ratio of the number of X chromosomes to the number of sets of autosomes. The Y chromosome in Drosophila is active but does not determine sex. It contains genes responsible for the production of sperms in adult flies.
Normal male Drosophila has a ratio of one X chromosome to two sets of autosomes. In contrast, normal female...
Normal male Drosophila has a ratio of one X chromosome to two sets of autosomes. In contrast, normal female...
9.9K
01:06Natural Selection and Mating Preferences
610
The principle of natural selection posits that organisms better adapted to their environment are more likely to survive and reproduce. This principle is closely intertwined with mating preferences, a key aspect of sexual selection, which evolutionary psychologists believe is driven by instincts to propagate one's genes. Such instincts significantly influence mating behaviors and preferences between genders.
Females, due to their biological roles in conception, pregnancy, and nursing,...
Females, due to their biological roles in conception, pregnancy, and nursing,...
610
02:19The Y Chromosome Determines Maleness
8.6K
The Y chromosome is a sex chromosome found in several vertebrates and mammals, including humans. In addition to 22 pairs of autosomes, the human males have one X chromosome and one Y chromosome. In these organisms, the presence or absence of the Y chromosome determines the development of male traits.
Evolution
Around 300 million years ago, the two sex chromosomes diverged from two identical autosomal chromosomes. Over time, the Y chromosome has lost most of its genes, shrinking in size....
Evolution
Around 300 million years ago, the two sex chromosomes diverged from two identical autosomal chromosomes. Over time, the Y chromosome has lost most of its genes, shrinking in size....
8.6K
01:23Criticisms of the Evolutionary Perspective
390
In a study where individuals posing as strangers offered compliments and proposed casual sex to students, the responses differed significantly based on gender. Not a single woman accepted the proposal, while 70% of the men agreed. This outcome provides a useful scenario to explore through the lens of evolutionary psychology and social learning theory, highlighting the diverse perspectives on human sexual behaviors.
Evolutionary psychology provides one explanation for these findings, suggesting...
Evolutionary psychology provides one explanation for these findings, suggesting...
390
01:19X-linked Traits
59.1K
In most mammalian species, females have two X sex chromosomes and males have an X and Y. As a result, mutations on the X chromosome in females may be masked by the presence of a normal allele on the second X. In contrast, a mutation on the X chromosome in males more often causes observable biological defects, as there is no normal X to compensate. Trait variations arising from mutations on the X chromosome are called “X-linked”.
59.1K
01:49Hardy-Weinberg Principle
76.8K
Diploid organisms have two alleles of each gene, one from each parent, in their somatic cells. Therefore, each individual contributes two alleles to the gene pool of the population. The gene pool of a population is the sum of every allele of all genes within that population and has some degree of variation. Genetic variation is typically expressed as a relative frequency, which is the percentage of the total population that has a given allele, genotype or phenotype.
76.8K