Their work appears online May 6 in advance of publication in the journal Nature Methods.
Fruit flies are well suited for chromosome studies because some of their cells contain gigantic, “polytene” chromosomes, each built up of more than 1,000 parallel copies of DNA strands. When stained, condensed, dark bands and lighter regions (interbands) give the chromosomes a striped appearance.
For more than 70 years, cytogeneticists have used a hand-drawn map of the bands of fruit fly polytene chromosomes, with the shape and location of these structures only vaguely delineated. This map, first published in 1935, and generations of light and electron micrographs have yielded an imprecise guide to the chromosomes.
Traditional methods of chromosome preparation have limited usefulness for those hoping to sort out how the bands and interbands relate to the underlying genetic sequence, said cell and developmental biology research specialist Dmitri Novikov, who developed the new technique. The genome of the fruit fly, Drosophila melanogaster, was sequenced in 2000, and yet its relationship to chromosome structure remains unclear.
“Since we want to know what genes are involved in the development of different structures in living systems, this is the first structure to look at,” Novikov said. “This is the starting point: the appearance of the genes themselves.”
Cell and developmental biology professor and lead investigator Andrew S. Belmont and visiting scientist Igor Kireev, of Moscow State University, are co-authors on the paper. Belmont is in the U. of I. Institute for Genomic Biology and the Center for Biophysics and Computational Biology.
Current methods for preparing polytene cells for viewing under a light microscope involve using a thumb, pencil, forceps or other instrument to maneuver and press the cells between a glass coverslip and slide. Only about 10 percent of the slides processed this way provide useable images and even those rarely offer crisp structural details, Novikov said.The new approach includes two components: the use of mechanical devices to spread and flatten the cells, and the application of computer-based image processing to analyze hundreds of examples of the same chromosomes. With so many crisp images to analyze, computer algorithms can accurately calculate the number, shape and location of the chromosome bands.
To improve chromosome spreading, researchers use a rotary tool that vibrates the coverslip surface for several minutes. A simple mechanical vise applies up to two tons of force to each slide, rendering the preparations very thin and high in contrast. This allows the production of much clearer, information-packed images.
The technique has other advantages: Because it relies on light microscopy, it is faster and more economical than electron microscopy, with comparable or superior results.
With a more accurate chromosome map, researchers will next use fluorescent immunostaining of proteins that bind to specific DNA sequences. These landmarks will help them tease out the relationship of the sequence to the physical structure.
The new approach will allow scientists to answer fundamental questions about chromosome structure, Novikov said. Such questions have relevance across species.
Editor’s note: To reach, call 217-333-8372; e-mail: email@example.com.
Diana Yates | EurekAlert!
The birth of a new protein
20.10.2017 | University of Arizona
Building New Moss Factories
20.10.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
20.10.2017 | Information Technology
20.10.2017 | Materials Sciences
20.10.2017 | Interdisciplinary Research