Directions: Genetic disorders are problems that occur on a genetic level.  “A genetic disorder is a disease that is caused by an abnormality in an individual’s DNA. Abnormalities can range from a small mutation in a single gene to the addition or subtraction of an entire chromosome or set of chromosomes,” (http://learn.genetics.utah.edu/content/disorders/whataregd/).  What that means is that there is something in a person’s genes, something that they inherited that causes the problem.  There are many types of genetic disorders, but for this assignment you are going to look at four different genetic disorders of two different types.

Chromosome Abnormalities
Chromosome abnormalities are disorders where there is an addition or subtraction of an entire chromosome or set of chromosomes.  The articles below look at two chromosome abnormalities: Down’s Syndrome and Klinefelter’s Syndrome.

Down’s Syndrome: http://learn.genetics.utah.edu/content/disorders/whataregd/down/index.html

Klinefelter’s Syndrome: http://learn.genetics.utah.edu/content/disorders/whataregd/klinefelter/index.html

Questions:

1. How do Down’s Syndrome and Klinefelter’s Syndrome occur?  In other words, what happens with the chromosomes when the gametes are forming?
2. Down’s Syndrome and Klinefelter’s Syndrome are both the addition of a chromosome.  Which chromosome is added for each condition?
3. For Klinefelter’s Syndrome, why are the symptoms that occur a logical consequence of the chromosome that is added.  Read the information carefully!

Single Gene Disorders
Single gene disorders are when a person inherits a gene from their parents that causes the disorder to occur.  Often these are recessive genes.  Read about the two single gene disorders below, and then answer the questions that follow.

Sickle Cell Anemia: http://learn.genetics.utah.edu/content/disorders/whataregd/sicklecell/index.html

Cystic Fibrosis: http://learn.genetics.utah.edu/content/disorders/whataregd/cf/index.html

Questions:

1. How does a child inherit sickle cell anemia or cystic fibrosis from non-sickle cell parents?
2. What does it mean to be a “carrier” of sickle cell anemia or cystic fibrosis?
3. Both the sickle cell allele and the cystic fibrosis allele are recessive.  The “normal” gene in each case is dominant.  Use Punnett Squares to determine the probability of the following parents having a child that is homozygous recessive for either disease: Mom – Dd; Dad – Dd.  In this case, D represents the dominant (normal) gene, and d represents the sickle cell or cystic fibrosis gene.