Biology/DNA
Advertisement
Question
Why is DNA shaped like a double helix?
DNA is usually made up of two complimentary strands of subunits. Each strand is made up of a chain of subunits. Each subunit is made up of a nitrogenous base, a deoxyribose sugar, and one or more phosphate groups. These subunits are bonded to each other with a phosphodiester bond, creating a single strand of DNA. Single strands of DNA hold no particular common shape as they tend to fold back upon themselves, forming structures based on their particular patterns of nucleotides. However, two complimentary strands of DNA (created by the cell through a process called DNA replication), held to each other by hydrogen bonds between the complimentary nucleotide bases, are more stable and fold predictably into the familiar double helix shape. This is a result of the molecular shape of the base pairs and the way with which they bond to the complimentary base pairs on the opposing strand. A lot of additional interesting information can be found here:
http://www.answers.com/topic/dna
Hope this helps!
-CB
Related Articles
Answers by Expert:
Chris Bemis
Expertise
I will answer questions relating to the identification of bacterial and fungal isolates using phenotypic (macroscopic/microscopic appearance, biochemical bench tests, fatty-acid analysis) as well as genotypic (RiboPrinting) methods. I can also answer questions relating to environmental microbiology, especially those specifically relating to the pharmaceutical industry. I am less familiar with clinical microbiology.
Experience
I have worked within the biotech industry for 9 years, most of that time spent in a Quality Control Microbiology laboratory setting.
Within the laboratory, I routinely performed bioburden testing; sterility testing; gel-clot and kinetic LAL testing; biological indicator testing; stability testing; microbial limits testing; media performance/growth promotion testing; microbial identifications testing using API, Vitek, MIDI (GC-MIS) and RiboPrinter identifications systems; total/fecal coliform testing; environmental monitoring; media preparation; stock culture maintenance; qualification of identification test kits and QuantiCult Plus organisms. I executed the QC validation of the DuPont Qualicon RiboPrinter Microbial Characterization System. I also supported sites internationally with the fungal/microbial identification process, the RiboPrinter assay, stock culture maintenance and the microbial identification process flow.
Organizations
Nationally Registered Microbiologist, American Society of Microbiology (2005)
Publications
Applied and Environmental Microbiology
Education/Credentials
B.S. in Microbiology (2000)
Awards and Honors
Received my company's 'Best Practice Award' for the Validation of the RiboPrinter Microbial Characterization System, 2004
©2012 About.com, a part of The New York Times Company. All rights reserved.