Genes come in pairs, and each gene in a pair may differ slightly. One gene may be dominant, and override the other gene, which is recessive. A recessive gene only has an effect if both genes in a pair are recessive. An example is eye color. Although this is not as simple as depicted here, blue is the recessive gene, and brown is the dominant gene.
Are you having a girl or a boy? Check out our video on the top 7 gender-predicting old wives' tales!