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This interrupted case is based on a genome wide association study (GWAS) that identified the genetic variation causing some inhabitants of the Solomon Islands to have blond hair. The case illustrates the connection between genotype and phenotype, and an application of Hardy-Weinberg equilibrium. The narrative focusses on John and his new roommate, Peter, from the Solomon Islands who happens to have dark skin and blond hair. Using thought-provoking questions students learn about the genetics and the biochemistry of the hair color trait and how a single genetic variation can influence phenotype. Is migration or mutation involved?  Upon completion of the activity students will know the source of the genetic variation that causes the blond hair phenomenon in the Solomon Islands and if it has any European origins. The case was written for an upper-level genetics course, but could also be adapted for introductory biology or for a genetics course for non-majors. An optional PowerPoint presentation with clicker questions is available for download from within the Answer Key.

Bipolar disorder is a common, complex genetic disorder, but the mode of transmission remains to be discovered. Many researchers assume that common genomic variants carry some risk for manifesting the disease. The research community has celebrated the first genome-wide significant associations between common single nucleotide polymorphisms (SNPs) and bipolar disorder. Currently, attempts are under way to translate these findings into clinical practice, genetic counseling, and predictive testing. However, some experts remain cautious. After all, common variants explain only a very small percentage of the genetic risk, and functional consequences of the discovered SNPs are inconclusive. Furthermore, the associated SNPs are not disease specific, and the majority of individuals with a "risk" allele are healthy. On the other hand, population-based genome-wide studies in psychiatric disorders have rediscovered rare structural variants and mutations in genes, which were previously known to cause genetic syndromes and monogenic Mendelian disorders.

That's why a paper published Thursday in the journal Genetics in Medicine is so remarkable. The paper identifies NGLY1 deficiency as an inherited genetic disorder, caused by mutations in the NGLY1 gene. The researchers have confirmed eight patients with these mutations who share several symptoms, including developmental delays, abnormal tear production and liver disease.

Newborn genetic screening is a health program that identifies treatable genetic disorders in newborn infants. Early intervention to treat these disorders can eliminate or reduce symptoms that might otherwise cause a lifetime of disability.

Genetically modified organisms (GMOs) or genetically engineered (GE) foods have the potential to cause a variety of health problems.  For example, they may produce new allergens and toxins, and spread harmful traits to non-GMO crops. In addition, at least one major environmental impact of genetic engineering has already reached critical proportions: overuse of herbicide-tolerant GE crops has spurred an increase in herbicide use and an epidemic of herbicide-resistant "superweeds," which will lead to even more herbicide use. The long-term impacts of GMOs are unknown, and once released into the environment they cannot be recalled.  

Parkinson's is a result of the loss of cells in various parts of the brain, including one portion that produces the neurotransmitter dopamine. Dopamine is essential for being able to move in a coordinated way, so the loss of dopamine causes the tremors often associated with the condition. While the exact cause of Parkinson's is unknown, genetics and environment are contributing factors. Most cases occur in patients with no family history of Parkinson's disease, but there are 13 gene mutations that have been linked to either causing the disease or increasing one's risk of developing it. Certainly not everyone who carries these gene mutations develops Parkinson's, but identifying these genetic indicators is the beginning of developing more precise treatments.

Jackson would eventually be diagnosed with the rare genetic eye disease Autosomal Dominant Neovascular Inflammatory Vitreoretinopathy (ADNIV), which eventually causes blindness in those who carry the gene.

Human-engineered microbes are workhorses of the pharmaceutical and chemical industries, churning out biofuels, drugs, and many other products. But they can cause big problems if they become contaminated by other microbes or viruses or escape into the environment. Now, a new type of microbe that can survive only on artificial nutrients promises better security against such mishaps. The strategy, described in two papers in this week's issue of Nature, might ultimately be used to control genetically engineered plants or other organisms released into the wild to create products or clean up pollution.

Since this time, research has focused on biological factors that may lead to autistic behaviours. This has found very clearly there is no one cause of autism. A variety of genetic factors are likely to be the ultimate cause of most cases of autism. These may work by themselves, or in combination with environmental factors, to lead a child's brain to develop differently and result in autistic behaviours.

Although genetic factors contribute to congenital heart disease, many children born with heart defects have healthy parents and siblings, suggesting that new mutations that arise spontaneously -- known as de novo mutations -- might contribute to the disease. New research shows that about 10 percent of these defects are caused by genetic mutations that are absent in the parents of affected children.

Over a million people in the United States have some form of Inflammatory Bowel Disease or IBD. It can be caused by intestinal bacteria, environment or genetics. One thing is for sure, the lining of the intestines don't work correctly because the cells have been disturbed by one of these things. A common finding in Crohn's and IBD is that a molecule called TNF is elevated, and starts the inflammation process. Researchers still don't know what signals the TNF to go up, but maybe they can turn it off with another molecule.

This case study presents the story of Phil, an undergraduate majoring in biology, whose Russian cousin Dimitri has contracted tuberculosis (TB) from inmates at the prison where he works.  Phil learns that his cousin's failure to complete his antibiotic regimen likely contributed to the evolution of antibiotic-resistant TB in his body.  Phil consults with his friend Stacy, and together they try to understand Dimitri's condition by applying what they are learning in their genetics lab experiment about the role of random mutation in bacterial evolution (including the development of antibiotic resistance) through Luria- Delbrück fluctuation analysis. The same analysis includes calculation of the mutation rate, which Phil realizes is sufficient to cause MRSA and other antibiotic-resistant infections. This case study was originally developed for concurrent use in freshman/sophomore-level genetics, elementary statistics, and precalculus. However, it is also very appropriate for courses in introductory biology, evolutionary biology, and biostatistics. The teaching notes discuss various ways to run the case depending on the mathematics and biology background of students.

"This modular case study tells the story of Dan and Annie, a married couple of Acadian ancestry who have a genetic form of deafblindness called Usher syndrome. They live in Southwest Louisiana, home of the largest population of DeafBlind citizens in the United States. Acadian Usher syndrome is caused by an allele of the USH1C gene that came to Louisiana with the first Acadian settlers from Canada who founded today's Cajun population. This allele's single nucleotide substitution creates an erroneous splice site that produces a defective cytoskeletal protein (harmonin) of the cochlear and vestibular hair cells and retinal photoreceptors. This splice site is the target of a promising gene therapy. The case study applies and connects Mendelian inheritance, chromosomes, cell division, vision and hearing, DNA sequences, gene expression, gene therapy and population genetics to a specific gene and its movement through generations of Dan and Annie's families.  After the introduction, each of the remaining sections can be used independently either for in-class team activities or out-of-class extensions or assignments over an entire year of introductory undergraduate biology. "

"This case study introduces students to Duchenne muscular dystrophy (DMD) and its underlying genetics, cell biology, and some of the associated biochemical pathways.  DMD is an X-linked disorder characterized by progressive muscle weakness and wasting due to the absence of a protein called dystrophin, which in turn causes degeneration of skeletal and cardiac muscle. There is currently no established cure for this disease.  The case follows the progress of "Casey," an undergraduate student who has just declared her biology major and is interested in expanding her scientific understanding of the different fields of biology. The case is organized in three parts: genetics, cell biology, and biochemistry, each exploring DMD through its unique lens. Throughout the case, Casey is presented with multiple outlets of information, including class lectures, direct e-mail interaction with a professor, scientific journals and websites, from which she (and any student engaged with the case) gathers knowledge about DMD."

Scientists are now one step closer to understanding how genetic mutations contribute to autism. In a study released Thursday in the journal Cell, experts from UNC School of Medicine discovered how one specific autism-linked gene mutation actually works

In the 2013 Holiday Lectures on Science, Charles L. Sawyers of Memorial Sloan-Kettering Cancer Center and Christopher A. Walsh of Boston Children's Hospital will reveal the breathtaking pace of discoveries into the genetic causes of various types of cancers and diseases of the nervous system, and discuss the impact of those discoveries on our understanding of normal human development and disease.

A single genetic mutation causes resistance to DDT and pyrethroids (an insecticide class used in mosquito nets), new research concludes. With the continuing rise of resistance, the research is key as scientists say that this knowledge could help improve malaria control strategies. The researchers used a wide range of methods to narrow down how the resistance works, finding a single mutation in the GSTe2 gene, which makes insects break down DDT so it's no longer toxic. They have also shown that this gene makes insects resistant to pyrethroids raising the concern that GSTe2 gene could protect mosquitoes against the major insecticides used in public health.

Over the last decade, as DNA-sequencing technology has grown ever faster and cheaper, our understanding of the human genome has increased accordingly. Yet scientists have until recently remained largely ham-fisted when they've tried to directly modify genes in a living cell. Take sickle-cell anemia, for example. A debilitating and often deadly disease, it is caused by a mutation in just one of a patient's three billion DNA base pairs. Even though this genetic error is simple and well studied, researchers are helpless to correct it and halt its devastating effects.

Researchers in a new study at the University of Edinburgh have honed in on five of 89 independent variations in human genetics that are believed to be responsible for autoimmune conditions, from celiac disease and multiple sclerosis to rheumatoid arthritis and asthma. Understanding how these mechanisms work could help scientists to develop new treatments. The team found that a mutation in the ADAR1 gene causes a defect in an "alarm system" in cells that normally protects the body from viruses and other infections by triggering the body's immune system to fight.

Huntington disease is caused by a mutation in the HTT gene. Understanding how the mutation causes neurodegeneration might help researchers develop treatments that protect brain function. This animation describes the genetic defect that underlies Huntington disease. Created by the editors at Nature Reviews Disease Primers.