Group items tagged

Sometimes, a genetic tweak can make a really big difference in an animal's appearance. That's what likely happened when the predecessors of modern snakes lost their legs, a process that started some 150 million years ago, two separate groups of scientists have discovered. Although the teams took very different approaches to solve the mystery of how those limbs vanished, both came up with similar results: Mutations in DNA located near a gene key to limb formation keep that gene from ever turning on, they report today.

In a first, scientists led by Kamel Khalili, director of the Comprehensive NeuroAIDS Center at Temple University, report in the journal Gene Therapy that they have for the first time successfully eliminated HIV genes from the genomes of mice and rats infected with the virus.

Researchers led by Terra D. Barnes of Washington University discovered that their genetically-engineered mice stutter due to DNA defects in a humdrum "housekeeping" gene. This gene codes for a protein that simply places a "routing tag" on certain enzymes that shred cellular trash. The tag ensures that the shredding enzymes end up in chambers called lysosomes, basically the cell's garbage disposal. It's a mundane cellular activity, yet mutations in the same process in humans have also been linked to stuttering-a bizarrely specific condition for such a general gene. And, so far, scientists have no idea why the two are linked.

In a study published Thursday in the journal Science, they report that they've pinpointed the bit of finch DNA behind the swift transition: a gene called HMGA2. In finches, HMGA2 seems to be the primary factor in beak size - like a really good group project leader, it orchestrates the expression of a number of other genes, each of which tweaks the size of the bird's beak. The same gene also appears in dogs, horses, even humans, holding sway over body size and stature.

In this case, developed for an introductory genetics class, students meet a woman whose family has a history of colon cancer. Students create a pedigree based on information from the case and discuss what it means to be genetically predisposed to cancer. Using bioinformatics tools from the NCBI database, students identify and examine the mutation in the woman's APC gene that results in genetic predisposition to colon cancer. Finally, they investigate the biological function of the APC protein to understand why this mutation contributes to the development of cancer and determine whether APC is a proto-oncogene, tumor suppressor gene, or genome stability gene.

Meiosis, the form of cell division unique to egg and sperm production, sets the stage for sex determination by creating sperm that carry either an X or a Y sex chromosome. But what is it about the X or Y that determines sex? Before a meiotic cell divides, its two sets of chromosomes come together and cross over, or swap, segments. The first animation shows normal crossing over, where the X and Y chromosomes exchange pieces only at their tips. The second animation shows a rare mistake in which the Y chromosome transfers a gene called SRY to the X chromosome, resulting in sex-reversed babies. Studies of sex-reversed individuals led researchers to identify the master switch for sex determination, the SRY gene, which tells a fetus to become a boy.

Meiosis, the form of cell division unique to egg and sperm production, sets the stage for sex determination by creating sperm that carry either an X or a Y sex chromosome. But what is it about the X or Y that determines sex? Before a meiotic cell divides, its two sets of chromosomes come together and cross over, or swap, segments. The first animation shows normal crossing over, where the X and Y chromosomes exchange pieces only at their tips. The second animation shows a rare mistake in which the Y chromosome transfers a gene called SRY to the X chromosome, resulting in sex-reversed babies. Studies of sex-reversed individuals led researchers to identify the master switch for sex determination, the SRY gene, which tells a fetus to become a boy.

Researchers have for the first time used electrical pulses delivered from a cochlear implant to deliver gene therapy, thereby successfully regrowing auditory nerves. The research also heralds a possible new way of treating a range of neurological disorders, including Parkinson's disease, and psychiatric conditions such as depression through this novel way of delivering gene therapy.

Quick look: In its modern sense, epigenetics is the term used to describe inheritance by mechanisms other than through the DNA sequence of genes. It can apply to characteristics passed from a cell to its daughter cells in cell division and to traits of a whole organism. It works through chemical tags added to chromosomes that in effect switch genes on or off.

Early-response genes, which are important for synaptic plasticity, are "switched off" under basal conditions by topological constraints. Neuronal activity triggers DNA breaks in a subset of early-response genes, which overrides these topological constraints, and "switches on" gene expression.

Learn to use Online Mendelian Inheritance in Man®, or OMIM®, a catalog of human genes and genetic conditions. OMIM is a foundational resource in genomics and is valuable for clinicians and biomedical researchers. OMIM links and data are found at sites all around the bioinformatics sphere, but understanding the full scope of OMIM's data and resources enable the most comprehensive understanding of human phenotypes and disease. OMIM contains full-text summaries of information from the scientific literature, and provides extensive links to the literature resources and other genomic resource tools as well. Use OMIM as a comprehensive first stop to find important information and gene links for human Mendelian disorders.

Within every cell in our body, two copies of a tumor suppressor gene called BRCA1 are tasked with regulating the speed at which cells divide. Michael Windelspecht explains how these genes can sometimes mutate, making those cells less specialized and more likely to develop into cancer.

The largest genome-wide association study to date, involving more than 300 institutions and more than 250,000 subjects, roughly doubles the number of known gene regions influencing height to more than 400. The study provides a better glimpse at the biology of height and offers a model for investigating traits and diseases caused by many common gene changes acting together.

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.

While humans and mice look and act very differently, 85 to 90 percent of our genes are the same or similar. So if scientists can understand the instructions in every mouse gene, people will get a good idea of the instructions in virtually every human gene as well.

Now, scientists at the Salk Institute for Biological Studies in La Jolla, Calif., have pinpointed a gene linked to these disorders that seems to be crucial for normal brain structure in prenatal development. The findings, which appear in an open-access article in the Jan. 14 issue of Cell Reports, shed new light on the mechanistic workings of a gene called MDGA1, previously implicated in autism, schizophrenia and bipolar disorder.

As the genomes of more and more species are sequenced, geneticists are piecing together an extraordinarily detailed picture of the molecules that are fundamental to life on Earth. With modern techniques, we can not only trace how the bodies of animals have evolved, we can even identify the genetic mutations behind these changes and, as we recently reported, genes sometimes evolve in surprising ways. Here though, in celebration of the versatility of DNA, New Scientist presents five classic examples of gene evolution.

Panobinostat is a new type of drug that works by blocking an enzyme responsible for modifying DNA at the epigenetic level. Epigenetics refers to chemical marks on DNA itself or on the protein "spools" called histones that package DNA. These marks influence the activity of genes without changing the underlying sequence, essentially acting as volume knobs for genes. Earlier genomic studies showed that about 80 percent of DIPG tumors carry a mutation that alters a histone protein, resulting in changes to the way DNA is packaged and tagged with those chemical marks. This faulty epigenetic regulation results in activation of growth-promoting genes that should have been turned off, and shutdown of others that should have acted as brakes to cell multiplication. Cancer is the result. Panobinostat appears to work by restoring proper functioning of the cells' chemical tagging system.

The mystery of where these orphan genes came from has puzzled scientists for decades. But in the past few years, a once-heretical explanation has quickly gained momentum - that many of these orphans arose out of so-called junk DNA, or non-coding DNA, the mysterious stretches of DNA between genes. "Genetic function somehow springs into existence," said David Begun, a biologist at the University of California, Davis.

This case study focuses on the relationship between evolution and plasticity using a hands-on, inquiry-based approach. Students view examples from the literature that illustrate the difference between nature and nurture, or the relative contributions of genes and the environment in shaping phenotypes. Using the Trinidadian guppy system as an example, students learn about seminal work in the field in addition to exploring quantitative genetic techniques used to partition phenotypic variance between genes (G) and the environment (E). They use real data from one of the publications cited in the case to graph reaction norms illustrating GxE interactions at the family and population level. The inquiry-based approach means that students are introduced to new concepts in a stepwise fashion, and asked to develop and build their understanding using causal, explanatory evidence. The case concludes with an exercise in which students apply their knowledge to a real conservation problem in Trinidad and Tobago, where guppies are native. This case would be appropriate for an upper level biology, genetics, or evolution course.

List of single gene traits in humans