Case Study:
http://www.sciencecases.org/
Like I said above, we had to create a pedigree based on what Greg and Olga told us about their families. To take a look at the pedigree I've created please follow the link below.
Greg and Olga Pedigree:
https://docs.google.com/
After we created the Pedigree we had to answer questions. The questions were pretty easy to answer once the pedigree was finished. Below are the Questions from pages 1-4 and my answers. I've colored the questions in green and my answers in blue.
Questions:
1) What would a pedigree of Greg and Olga’s families look like? Concentrate simply on family relationships and affected persons.
2) Do autosomal dominant disorders skip generations?
Yes. In Olga’s side of the family it skipped generations but in Greg’s side it skipped but his brother ended up with hemophilia insteas of mytonic dystrophy (MD).
3) Could Greg or his mother be carriers of the gene that causes myotonic dystrophy?
It is possible that Greg’s mom could be a carrier for (MD) because her sister and brother contain a gene. Greg on the other hand probably not because neither his sister or brother contain the (MD) gene but his brother has the Hemophilia gene.
4) Is there a possibility that Greg’s aunt or uncle is homozygous for the myotonic dystrophy (MD) gene?
There is a possiblitity that Greg’s aunt and uncle could be homozygous for containing the gene. Their parents don’t but they could.
5) Symptoms of myotonic dystrophy sometimes don’t show up until after age fifty. What is the possibility that Greg’s cousin has inherited the MD gene?
Greg’s cousin has a 50% probability of having the MD gene since her mother carries it.
6) What is the possibility that Greg and Olga’s children could inherit the MD gene?
The possibility that their child can inherit the MD gene is 0% because Greg is not a carrier of the MD gene and neither is Olga.
7) What are the hallmarks of an autosomal recessive trait?
The hallmarks of an autosomal ressive trait are in almost every family member because both parents do not have the gene only one parent does.
8) What does consanguineous mean? Why is this concept especially important when discussing recessive genetic disorders?
Consanguineous means having the same ancestry or descent; related by blood. This concept is important because Greg and Olga could carry the same gene without even knowing it.
9) What is it about the inheritance pattern of factor VIII deficiency seen in Greg and Olga’s pedigree that point toward it not being an autosomal recessive trait?
The pattern of factor VIII (Hemophilia) skips a generation and in Greg’s family it was only contained by his brother.
10) What are the characteristics of X-linked recessive inheritance?
The characteristics can sometimes be only found in males who have inherited a ressive X-link mutated from their mother.
11) Why does a son never inherit his father’s defective X chromosome?
If the baby is going to be a son he can recive and X from his mother but in order to be a boy the son needs to receive a Y from the father because the male only carries XY and females carry XX. If the baby were to receive a defective X chromosome from his father then the baby would be a girl because the mom can only give and X.
12) What is required for a woman to display a sex-linked recessive trait?
For a woman to display an X-linked recessive trait, she would need two mutant copies of the X-chromsome--one from both parents.
13) Return to the pedigree drawn earlier for Greg and Olga; mark those persons who are carriers of the factor VIII deficiency gene.
The people who are marked for the Factor VIII definiency gene are the ones marked in yellow.
14) What is the chance that Olga carries the gene for factor VIII deficiency? Calculate the probability that she will pass it to her offspring. Will male children be affected in a different way than female children?
Olga has a ¼ chance of carrying the gene of Factor VIII. Therefore she has a ¼ chance of passing it to her offspring. The male child has a 1/8 chance of being affected or of being a carrier. It is the same change for female children.
15) What is the chance that Greg carries the factor VIII gene? Can he pass the gene on to his sons? His daughters? How will each be affected?
Factor VIII is carried by an X chromosome so there is no chance that Greg has the affected gene. He can not pass it to his son because he must pass a Y chromosome inorder to have a son. For his daughter, she can not be affected because he carries the unaffected X chromosome.
