In addition to C. elegans and Drosophila, Zebrafish are also another model organism - and have a spine. We're interested in two phenotypes, a curved spine and a gene that causes skin tumors to form on the fish's skin. We'd like to know if we could use the curved spine as an indicator if a fish may develop tumors (if the genes are linked). We'll assume that each of these traits is controlled by a single gene where: a curved spine is the result of a dominant allele S (and a normal spine is the result of recessive alleless), ⚫ and tumor growth is the result of a recessive allele t (and no tumor growths are a dominant T allele). A testcross is performed with a fish that is heterozygous for both genes and the resulting progeny are given below. TtSs x ttss curved spine & no tumors curved spine & tumors normal spine & no tumors 27 45 normal spine & tumors 30 SUN 50 Are these two genes following Mendelian inheritance patterns? Use Chi-Squared analysis to test them. x2 = (0-6)² 1. X2 value: type your answer... 2. Degrees of Freedom: type your answer.... Table 11.5 Chi-Square Probabilities Probabilities df 0.95 0.90 0.70 0.50 0.30 0.20 0.10 0.05 0.01 0.001 1 0.004 0.016 0.15 0.46 1.07 1.64 2.71 3.84 6.64 10.83 3. p-value type your answer... 2 0.10 0.21 0.71 1.39 2.41 3.22 4.61 5.99 9.21 13.82 3 0.35 0.58 1.42 2.37 3.67 4.64 6.25 7.82 11.35 16.27 4 0.71 1.06 2.20 3.36 4.88 5.99 7.78 9.49 13.28 18.47 4. Determination: YES they appear mendelian, or NO they appear to be non-mendelian type your answer... 5 1.15 1.61 3.00 4.35 6.06 7.29 9.24 11.07 15.09 20.52 1.64 2.20 3.83 5.35 7.23 8.56 10.65 12.59 16.81 22.46 5. Assume for a moment that these genes are linked. If so, what allele combinations are parental in the TtSs genotype listed in the cross? type your answer...

Theodor Boveri predicted that malignancies would often be associated with chromosomal mutation. What lines of evidence substantiate this prediction?

Two genes associated with breast cancer, BRCA1 and BRCA2, were discovered in 1994 and 1995, respectively, and shortly thereafter, were patented by Myriad Genetics, a company based in Utah. Under the patents, testing for mutations in these genes could only be performed by Myriad, at costs from 300 to 3,000. Myriad also patented the process of analyzing the results of such tests, preventing anyone who obtains the sequence of their BRCA genes by other means (which itself would probably be patent infringement) from interpreting the information. The idea that genes can be patented has been a contentious issue from the beginning. Patents are not granted for products of nature, meaning that genes inside the body are not patentable, but biotech companies successfully argued that by removing a gene from the human body, purifying it, and then obtaining its DNA sequence, they created something not found in nature, and which is therefore a patentable invention. The U.S. Patent Office found the argument persuasive, but opponents argue that genes are parts of our bodies and can be identified but not invented. Biotech companies argue that without the protection offered by patents, they would have no incentive for research and development of diagnostic tests. In Europe, patents for BRCA1 and BRCA2 were revoked in 2004 because they did not meet the standards for a patent. After more than a decade of legal disputes, the patents were partially restored in 2008 on a very restricted basis. In the United States, a lawsuit, focused on the patents for the BRCA genes, was filed in May 2009. The suit challenges the basic idea that genes are patentable. In November 2009, the judge ruled that the lawsuit can proceed, and the case is moving forward. In March 2010, a federal court invalidated Myriad Genetics patent on these genes. In August 2011, the U.S. Court of Appeals reversed the lower courts decision and ruled that gene sequences isolated from cells are not a product of nature and are therefore patentable. The case went to the U.S. Supreme Court, which ordered the appeals court to reconsider the case. The Federal Appeals Court did not change its decision, and the case once again, went to the U.S. Supreme Court. A unanimous decision in June 2013 invalidated Myriads patents on the basis that isolating a gene from nature does not make it patentable. This is a landmark decision on gene patenting with widespread ramifications for the biotechnoloogy industry. Will this decision reduce the incentives for companies to invest in new diagnostic tests that would be used by cancer victims or those with serious genetic disorders?

One unexpected result of the sequencing of the human genome was the finding that mutations in a single gene can be responsible for multiple distinct disorders. For example, mutations in the RET gene can cause two different types of multiple endocrine neoplasias, familial medullary thyroid carcinoma, and Hirschsprung disease. How do you think mutations in a single gene can have such diverse effects?