3.  Cause: Patient has three copies of the 21 st chromosome instead of two  Known as Trisomy 21  Symptoms: Lifelong mental retardation and developmental delays http://abcnews.go.com/Health/video/livi ng-with-down-syndrome-15483374

4.  Cause: Woman has only one X chromosome  Having only one copy of a chromosome is called monosomy  Symptoms: short in height, failure to begin puberty, infertility, heart defects, and learning disabilities

5.  Cause: Man with more than one X chromosome  Symptoms: Negatively affects testicular growth, which can lead to lower production of testosterone. May also cause reduced muscle mass, reduced body and facial hair, and enlarged breast tissue.

7.  Cause: Defect in the gene that enables your body to produce a protein that helps give connective tissue its elasticity and strength  Symptoms: Affects connective tissue most commonly in the heart, eyes, blood vessels and skeleton. Causes individual to be tall and thin with disproportionately long arms, legs, fingers and toes. http://www.youtube.co m/watch?v=E_98wTAZNy M

8.  Cause: defect in the genes affecting height  Symptoms: dwarfism http://www.youtube.com/watch?v=yfxB1 dDBXtY

9.  Cause: mutation in the gene that tells your body to make hemoglobin, the oxygen carrying compound found in your blood.  Symptoms: red blood cells become rigid, sticky and crescent shaped. These irregularly shaped cells can get stuck in small blood vessels, which can slow or block blood flow and oxygen to parts of the body.

10.  Cause: Mutation in the gene that holds the nucleus of each cell together  Symptoms: rapid aging http://www.yout ube.com/watch? v=LvvxHjon_3E

11.  Cause: Mutation of the gene used in the production of melanin  Symptoms: lack of pigmentation http://www.youtube.com/watch?v=OQoa F6t5QH0

13.  Cause: Sex-linked recessive disorder  Symptoms: Blood does not clot properly http://www.youtube.com/watch?v=BZN9s kFmKTg

14.  Cause: Sex-linked recessive disorder  Symptoms: weak muscles http://www.yout ube.com/watch?v =ZrPnmgs4rHM