In Sickness and in Health Genetic Counseling

The pedigree for Greg's Family 




This is an example of an autosomal dominant inheritance pattern.

 



The Pedigree for Olga's Family

        Many people wonder well could our kids develop the same diseases that run in our family? Greg and Olga were wondering the same thing. Well it's all genetics!!! For the Sickness and Health Genetic Counseling Greg and Olga went to the genetic's counselor because they were worried about having kids because they were concerned whether or not their kids will have myotonic dystrophy or factor VIII. Autosomal dominant disorders don't skip generations. So, Greg and his mother couldn't be factors of the gene that causes myotonic dystrophy. There is not a possibility that Greg's aunt or uncle could be homozygous for the myotonic dystrophy because they only got one copy. So, they are both heterozygous. There is not a possibility that Greg's cousin has inherited the myotonic dystrophy gene. Greg and Olga's children won't have myotonic dystrophy because Greg doesn't have the disease. The five hallmarks of autosomal recessive traits are females and males are equally likely to be affected, on average, the recurrence risk to the unborn sibling of an affected individual is one out of four, the trait is characteristically found in siblings, not parents of affected or the offspring of affected, and parents of affected children may be related. Autosomal recessive traits do skip generations.

      The rarer the trait in the general population, the more likely a consanguineous mating is involved, and the trait can appear as an isolated event in small sibships. Consaguinity is when there is a possibility of one parent being a carrier, with the recessive allele being passed through the carrier offspring and by producing an affected homozygous offspring generations later on. This is important when relating to autosomal recessive inheritance because in order for a child to be a carrier of a disease they must receive a recessive allele from both of his or her parents. The inheritance pattern of the factor VIII deficiency that is recognized in Olga's and Greg's pedigree shows that it is not an autosomal recessive trait because it is a sex-linked trait, because only guys get it. Greg's brother had it and Olga's brother had this disease. Some of the characteristics of X-linked recessive inheritance is that the disease is never passed from father to son, and this trait or disease is usually passed from an affected grandfather, through his carrier daughters, to half of his grandsons.  A son never inherits their father's defective X-chromosome, because they only inherit their father's Y-chromosome. When the mother is a carrier she will pass the affected X-chromosme to her son only one half of the time, and her daughters will not be affected because they always get a normal X-chromosome from their father.

                               

     There isn't a possibility that Greg carries the factor VIII gene, but if he did he couldn't be a carrier. There is a possibilty that Olga carriers the factor VIII gene, but it depends upon which of her mother's X chromosomes she inherited. So, her sons would be affected one half of the time but her daughters would not be affected. Olga has a one in twenty three chance of carrying the cystic fibrosis gene. Since, Greg is Asian American and within his population group the carrier frequency is 1 out of 180.  So, the possibility of producing a baby with cystic fibrosis would be 1 out of 16,560. So there chances are very slim of having a kid with that disease. The equation P+q=1 describes all of the alleles in the population. The percentage of the healthy people represents the p. The rest of the alleles must have the disease causing form which represents the q. If p is .65, then q is the other alleles that must be the disease causing form which is .35. Then, p+q=1. In all, I understand about the characteristics of autosomal dominant traits, autosomal recessive traits, and sex-linked traits.