Mother’s Reproductive System Influences Sex of the Offspring: Study

The female reproductive system can identify if the sperm can produce a girl or boy child before fertilizing the egg, finds a study.

It is known that a sperm dictates the sex of the offspring. Recently, researchers from the University of Sheffield found female pigs unconsciously influence the sex of the offspring by altering the environment in the oviduct to enable only sperm of a specific sex to reach the egg for fertilization.

 In nature, males and females play 50-50 role in influencing the genes and gender of the fertilized egg. Past trials on humans and animals suggest maternal age, exposure to disastrous events like war and famine impact the sex ratio of the offspring. However, the studies could not clearly explain the mechanisms responsible for varied influences on gender of the fertilized zygote.

Many types of gene remain active in the pig's reproductive system in the presence of all X (female) and all Y (male) sperms. When the sperms enter the fallopian tubes, the conditions inside it favor only one sperm of particular sex and destroy the remaining.  

For the current study, experts inseminated female pigs with sperms that were either completely X or Y and examined the gene expressions within the fallopian tubes. They observed in the presence of X or Y sperm, nearly 501 genes in the oviduct continuously produced proteins in different quantities. But the researchers were unable to point out the reasons for these responses to the sperms of different sexes and the mechanisms that led to the evolution of this trait in females.

"What this shows is that mothers are able to differentiate between the sperm that makes boys and girls. That on its own is amazing. It's also of great scientific and evolutionary importance. If we understand how they can do that, this can revolutionize the field," said Alireza Fazeli, study author and researcher from the Department of Human Metabolism at the University of Sheffield in a news release.

The study authors believe in investigating further.

More information is available online in the journal BMC Genomics.