The factors are usually both genetic and environmental, where a combination of genes from both parents, in addition to unknown environmental factors, produce the trait or condition. There appears to be a different threshold of expression , which means that one gender is more likely to show the problem over the other gender. For example, hip dysplasia is nine times more common in females than males.
Multifactorial traits do recur in families, because they are partly caused by genes.
The chance for a multifactorial trait or condition to happen again depends upon how closely the family member with the trait is related to you. For example, the risk is higher if your brother or sister has the trait or disease, than if your first cousin has the trait or disease. Family members share a certain percentage of genes in common, depending upon their relationship. As you can see, the more genes you have in common with the family member, the higher the chance for you to have a child with a similar defect. Height Height is determined by both genetic and environmental factors.