Pedigree Analysis Inheritance of Genetic Disorders PDF

Titu Maiorescu University Faculty of Dental Medicine Specialization: Dental Medicine Genetics, year 2 Pedigree analysis. Inheritance of genetic disorders Inheritance Patterns  Autosomal dominant disorders;  Autosomal recessive disorders;  X-linked recessive di...

Titu Maiorescu University Faculty of Dental Medicine Specialization: Dental Medicine Genetics, year 2 Pedigree analysis. Inheritance of genetic disorders Inheritance Patterns  Autosomal dominant disorders;  Autosomal recessive disorders;  X-linked recessive disorders;  X-linked dominant disorders;  Y-linked disorders;  Mitochondrial disorders. Autosomal dominant inheritance  “Autosomal” means that the gene in question is located on one of the numbered, or non-sex, chromosomes;  “Dominant” means that a single copy of the mutated gene is enough to cause the disorder → anyone who inherits one dominant disease mutation will have that disease;  If the trait is displayed in offspring, at least one parent must show the trait;  Occurs in every generation;  Dominant mutations can also happen in an individual for the first time, with no family history of the condition (spontaneous mutation);  The recurrence risk is high: 50% if one parent is heterozygous, 75% if both parents are heterozygous, and 100% if one parent is homozygous dominant; Autosomal recessive inheritance  “Recessive” means that two copies of the mutated gene (one from each parent) are required to cause the disorder.  Males and females have the same chance of expressing the trait.  Can skip generations.  In a family where both parents are carriers and do not have the disease, roughly a quarter of their children will inherit two disease-causing alleles and have the disease - two carriers have 25% chance of having an affected child with two changed genes.  Titu Maiorescu University Faculty of Dental Medicine Specialization: Dental Medicine Genetics, year 2 X-linked dominant inheritance  A mutation in one copy of an X-linked gene will result in disease for both males and females.  Families with an X-linked dominant disorder often have both affected males and affected females in each generation.  Fathers cannot pass X-linked dominant conditions to their sons, but all daughters of affected fathers will be affected with the condition and can pass it on to their children. X-linked recessive inheritance  Males are more frequently affected.  One copy is sufficient to cause the disease in males, but both copies are needed to cause the disease in females - if one mutant copy is present, the normal copy can compensate for the changed copy).  In X-linked recessive inheritance, a daughter inherits a single mutated gene on the X chromosome from one of her parents.  The X chromosome she inherits from the other parent will usually cancel the effect of the mutation, and she most likely will not have the genetic condition.  The female is only a HEALTHY CARRIER Y-linked inheritance  Trait expression and transmission is only in males, the individuals with the Y chromosome Mitochondrial  Can affect both males and females, but only passed on by females because all mitochondria of all children come from the mother; can appear in every generation.