"47,XYY Syndrome." Genetics Home Reference. N.p., n.d. Web. 18 Apr. 2015. "Conditions." Kaiser Permanente Genetics Northern California. N.p., n.d. Web. 18 Apr. 2015. "XYY Syndrome." Healthline. N.p., n.d. Web. 18 Apr. 2015. Xyy Syndrome Is A Genetic Condition That Is Caused By An Extra Chromosome. To, Understand What Xyy Syndrome Is, It Is Helpful To Know Something About Genes And, and Chromosomes.XYY Syndrome What Is XYY Syndrome? (n.d.): n. pag. Web. "Xyy+syndrome - Google Search." Xyy+syndrome - Google Search. N.p., n.d. Web. 18 Apr. 2015.