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Why does a snake have 25 or more rows of ribs, whereas a mouse has only 13? The answer, according to a new study, may lie in "junk DNA," large chunks of an animal's genome that were once thought to be useless. The findings could help explain how dramatic changes in body shape have occurred over evolutionary history. Scientists began discovering junk DNA sequences in the 1960s. These stretches of the genome-also known as noncoding DNA-contain the same genetic alphabet found in genes, but they don't code for the proteins that make us who we are. As a result, many researchers long believed this mysterious genetic material was simply DNA debris accumulated over the course of evolution. But over the past couple decades, geneticists have discovered that this so-called junk is anything but. It has important functions, such as switching genes on and off and setting the timing for changes in gene activity. 

In the August 1 issue of CELL, researchers from the Gene and Stem Cell Therapy Program at Sydney's Centenary Institute revealed another function of introns, or noncoding nucleotide sequences, in DNA. They reported that gene-sequencing techniques and computer analysis allowed them to demonstrate how granulocytes use noncoding DNA to regulate the activity of a group of genes that determines the cells' shape and function.

DNA has a double helix structure. If untwisted, DNA looks like two parallel strands. Each strand has a linear sequence of A, C, G, and T. The precise order of the letters carries the coded instructions. One strand is a complementary image of the other: A always pairs with T, and C always pairs with G.

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.

Your genome, every human's genome, consists of a unique DNA sequence of A's, T's, C's and G's that tell your cells how to operate. Thanks to technological advances, scientists are now able to know the sequence of letters that makes up an individual genome relatively quickly and inexpensively. Mark J. Kiel takes an in-depth look at the science behind the sequence.

Your genome, every human's genome, consists of a unique DNA sequence of A's, T's, C's and G's that tell your cells how to operate. Thanks to technological advances, scientists are now able to know the sequence of letters that makes up an individual genome relatively quickly and inexpensively. Mark J. Kiel takes an in-depth look at the science behind the sequence.

This Click and Learn explains how DNA sequences can be used to generate such trees, and how to interpret them.

Paul Strode describes the HHMI BioInteractive Click and Learn activity on DNA sequencing and phylogenetic trees. He describes how it teaches students DNA sequence alignment, and how those sequence differences allow researchers to determine relationships between species. Visit www.biointeractive.org/phylo-tree to use the interactive resource, and to find related materials. Subscribe to the BioInteractive YouTube channel to get the latest educator tips!

Interactive requiring shockwave:  Replicate DNA, transcribe and translate a sequence of virtual DNA.  Reading and information includied.  Good webquest component.

A gene mutation is a permanent alteration in the DNA sequence that makes up a gene, such that the sequence differs from what is found in most people. Mutations range in size; they can affect anywhere from a single DNA building block (base pair) to a large segment of a chromosome that includes multiple genes.

New research shows our DNA is absolutely loaded with... NOTHING. 98 percent of our DNA plays no role in our development. But as Trace learns, the findings may not be so black and white.

This video segment adapted from NOVA scienceNOW examines the realm of personal DNA testing. It describes the latest tests, which look for single-nucleotide polymorphisms (SNPs). These single-letter differences in DNA sequence make humans unique from one another but may also predispose people to certain diseases. The video also discusses the Personal Genome Project, an extension of the Human Genome Project aimed at determining the root causes of many common diseases. The Personal Genome Project takes into account personal genomics as well as lifestyle information, such as one's living environment, habits, and behaviors.

By early 2014, Flint, Kendler and a team of collaborators had analysed DNA sequences from 5,303 Chinese women with depression, and another 5,337 controls. As Flint expected, 85% of the depressed women had a severe form of the disorder called melancholia, which robs people of the ability to feel joy. "You can be a doting grandparent and your favourite grandchildren can show up at your door," says Douglas Levinson, a psychiatrist at Stanford University in California, "and you can't feel anything." The analysis yielded two genetic sequences that seemed to be linked to depression: one in a stretch of DNA that codes for an enzyme whose function is not fully understood, and the other next to the gene SIRT1, which is important for energy-producing cell structures called mitochondria. The correlations were confirmed in another set of more than 3,000 depressed men and women and over 3,000 controls.

Autism is rooted in genetics, including the mutation of certain genes that result in a failure of neurons in the brain to properly connect. Based on earlier genetic research funded by Autism Speaks, such as the Autism Genome Project (AGP), scientists have discovered some of these genes. But much more gene discovery needs to take place. The Autism Genome 10K Project will mark a substantial leap forward on this journey. The Autism Genome 10K Project builds on the successes of Autism Speaks' Autism Genetic Resource Exchange program (AGRE), a high-quality collection of more than 12,000 DNA samples from families affected by autism. The AGRE program has facilitated many high-impact scientific discoveries in recent years, including the risk genes discovered by the AGP and other researchers. With BGI sequencing the full complement of 10,000 samples collected by AGRE and collaborators in China, Autism Genome 10K leverages BGI's cutting-edge expertise and globally unrivaled capacity for high-quality genome sequencing.

Lying dormant in our genomes are millions of jumping genes. Originally discovered by Barbara McClintock, transposons are DNA sequences that can move from one location to another in our DNA. Transposons cause mutations when they jump to new locations, so keeping them from jumping is important. 

3:27 video introduces genetics and DNA sequence

This interrupted case study examines molecular genetic evidence reported in scientific literature to determine the fate of Louis-Charles, son of Louis XVI and Marie-Antoinette of France. Controversy and rumors surrounding the death of Louis-Charles suggested that either he died as a young boy while being held in captivity by the French revolutionaries or he escaped and was replaced by a substitute who died in his place. One individual claiming to be Louis-Charles was Karl Naundorff. Students begin the case by preparing pedigrees for the descendants of Maria Theresa and Francis I, the Holy Roman Emperor, parents of Marie-Antoinette. The pedigrees can be used to introduce the concepts of alleles identical-by-descent and cytoplasmic inheritance patterns. Students then compare mitochondrial DNA sequences and XY chromosome sequences from hair, bone, heart, and blood samples taken from descendants of Marie Theresa, Karl Naundorff and the heart of the boy who died in captivity to determine if the latter was truly Louis-Charles. An optional PowerPoint presentation with clicker questions is available to help guide the classroom activities.

High quality real time animations of processes

Almost every cell in your body has the same DNA sequence. So how come a heart cell is different from a brain cell? Cells use their DNA code in different ways, depending on their jobs. Just like orchestras can perform one piece of music in many different ways. A cell's combined set of changes in gene expression is called its epigenome. This week Nature publishes a slew of new data on the epigenomic landscape in lots of different cells. Learn how epigenomics works in this video. Read the latest research on epigenetics at http://www.nature.com/epigenomeroadmap

"Biologists and informaticists at Indiana University have produced one of the most extensive pictures ever of mutation processes in the DNA sequence of an organism, elucidating important new evolutionary information about the molecular nature of mutations and how fast those heritable changes occur."