B. What genes are involved in inactivating a human X chromosome?

Control of gene expression in eukaryotic cells occurs at which level(s)? a. only the transcriptional level b. epigenetic and transcriptional levels c. epigenetic, transcriptional, and translational levels d. epigenetic, transcriptional, post-transcriptional, translational, and post-translational levels

Equalizing the Expression of X Chromosome Genes in Males and Females Individuals with an XXY genotype are sterile males. If one X is inactivated early in embryogenesis, the genotype of the individual effectively becomes XY. Why will this individual not develop as a normal male?

Through alternative splicing, eukaryotes (a) reinforce gene inactivation (b) prevent transcription of heterochromatin (c) produce related but different proteins in different tissues (d) amplify genes to meet the requirement of high levels of a gene product (e) bind transcription factors to enhancers to activate transcription

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?

When two protein-coding genes have very similar nucleotide sequences and are located right next to each other on a chromosome, we can hypothesize that: a. one of them is a duplicate of the other, copied by aretrotransposon. b. they are nonhomologous. c. one of them is a pseudogene. d. they were produced by unequal crossing-over. e. they are transcribed in the same cell types.

Equalizing the Expression of X Chromosome Genes in Males and Females Males have only one X chromosome and therefore only one copy of all genes on the X chromosome. Each gene is directly expressed, thus providing the basis of hemizygosity in males. Females have two X chromosomes, but one is always inactivated. Therefore, females, like males, have only one functional copy of all the genes on the X chromosome. Again, each gene must be directly expressed. Why, then, are females not considered hemizygous, and why are they not afflicted with sex-linked recessive diseases as often as males are?

What does the ob gene code for? How does it work? Is this a gene found only in animals, or do humans have it also?

Homeobox genes (a) are found in fruit flies but no other animals (b) tend to be expressed in the order that they appear on a chromosome (c) contain a characteristic DNA sequence (d) b and c (e) a, b, and c

The cystic fibrosis gene encodes a chloride channel protein necessary for normal cellular functions. Let us assume that if at least 5% normal channels are present, the affected individual has mild symptoms of cystic fibrosis. Having less than 5% normal channels produces severe symptoms. At least 50% of the channels must be expressed for the individual to be phenotypically normal. This gene has various mutant recessive alleles: Predict the percent of functional channels and severity of symptoms for the following genotypes: a. heterozygous for CF100 b. homozygous for CF100 c. heterozygous, with one copy of CF100 and one of CF3 d. heterozygous, with one copy of CF1 and one copy of CF3