GENETIC DISORDERS & DISEASES

Types?  Dominant  Recessive  Sex Linked  Chromosomal  Mutagens?

 In some genetic conditions, inheriting just one copy of the mutated gene is enough to cause the disease  These are called dominant genetic disorders; the abnormal gene dominates no matter what the second copy of the gene is.  If gene is not inherited, can not be passed to children  Recessive Genes can be passed on even if the parent did not have the condition

Huntington’s Disease  Progressively damages the brain and central nervous system  Symptoms do not usually appear until middle age  Problems?  Passed on by this point…  1 in 2 chance of inheriting the disease

 Some dominant conditions vary in severity form person to person  Some are affected while others only mildly so or more strongly expressed; Variable Penetrance  Examples of Dominant Singe Gene disorders: - Adult polycystic kidney disease - Huntington’s disease - Cleft chin - Phenylketonuria - Neurofibromatosis - Achondroplasia

Recessive Inheritance Pattern  In order to have the disease, one would have to inherit two copies (alleles) of the abnormal gene, one from each parent  Cystic Fibrosis  Thalassemia; Alpha & Bata, Sickle-Cell  Albinism

Recessive Genes  Can be passed down form generation o generation by people who carry one normal & one copy of gene  Often unaware of carrying gene  Once two carriers have a child, condition emerges in the baby  ¼ chance child will be born with the disease

Sex-linked Conditions  Fragile X Syndrome  Hemophilia  Duchene Muscular Dystrophy  Color-blindness  Hairy ears

Chromosome Disorders  Abnormalities in the normal group of 46 chromosomes that we inherit form parents  More or fewer chromosomes?  Structural Changes?  Trisomy's?  Down’s Syndrome?  Klinefelter’s Syndrome  Cri du Chat (cat’s cry) Syndrome  Williams Syndrome

Pregnant mother may be referred for screening if:  Already has a child with an inherited genetic condition  There is or may be a genetic condition in her or the fathers family  She or the fathers belong to an ethnic community in which particular conditions are more common: - Thalassemia (Pakistani/Indian) - Sickle Cell Anemia (African/Caribbean) - Tay-Sachs Disease (Certain Jewish)