A man with more brothers will have a son and a man with more sisters will have daughter. A new research claimed that the genes of a man determine if it is going to be a son or a daughter.
Corry Gellatly and his team from the Newcastle University worked on 927 family trees to come to this conclusion. They studied about 556,387 people from North America and Europe dating back to 1600. He said that the analysis of the family tree showed that men who have more brothers are likely to have sons and those having more sisters are likely to have daughters. He also noted that this could not be predicted in women.
Men determine the sex of a child. An X chromosome of the father combines with the mother’s X chromosome to make a baby girl (XX) and a Y chromosome combines with mother’s to make a boy (XY). Gene consists of two parts known as alleles and inherited one from each parent.
In the study, Gellatly says that men are likely to carry two different types of allele. They said that men with ‘mm’ combination produce more Y sperm and have more sons. The men with ‘mf’ combination produce equal number of X and Y sperm and have an approximately equal number of sons and daughters. And men with ‘ff’ combination produce more X sperm and have more daughters, the study said.