Day 2, April 4, 2008

We constructed the pedigree for Mr. and Mrs. Smith. We then continued by looking up extra information to better understand how genetic diseases are transferred from parents to children.

• With the understanding that almost all affected individuals are heterozygotes, and that in most matings involving a person with an autosomal dominant trait the other partner will be homozygous normal, there are four hallmarks of autosomal dominant inheritance.
  Except for new mutations, which are rare in nature and extremely rare on examination pedigrees, and the complexities of incomplete penetrance to be discussed later, every affected individual has an affected biological parent. There is no skipping of generations.
  Males and females have an equally likely chance of inheriting the mutant allele and being affected. The recurrence risk of each child of an affected parent is 1/2.
  Normal siblings of affected individuals do not transmit the trait to their offspring.
  The defective product of the gene is usually a structural protein, not an enzyme. Structural proteins are usually defective when one of the allelic products is nonfunctional; enzymes usually require both allelic products to be nonfunctional to produce a mutant phenotype.
  http://www.uic.edu/classes/bms/bms655/lesson3.html

Hallmarks of x-linked recessive inheritance:

• As with any X-linked trait, the disease is never passed from father to son.
• Males are much more likely to be affected than females. If affected males cannot reproduce, only males will be affected.
• All affected males in a family are related through their mothers.
• Trait or disease is typically passed from an affected grandfather, through his carrier daughters, to half of his grandsons.
• Retrienved from: http://www.uic.edu/classes/bms/bms655/lesson7.html

Hallmarks of Autosomal Recessive Inheritance:

• Males and females are equally likely to be affected.
• On average, the recurrence risk to the unborn sibling of an affected individual is 1/4.
• The trait is characteristically found in siblings, not parents of affected or the offspring of affected.
• Parents of affected children may be related. The rarer the trait in the general population, the more likely a consanguineous mating is involved.
• The trait may appear as an isolated (sporadic) event in small sibships.
• Retrieved from:
  http://www.uic.edu/classes/bms/bms655/lesson5.html