Dna why double helix

Determining the structure of DNA was based in part on the work of many other scientists, including Rosalind Franklin. Molecules with a helical shape have this type of X-shape pattern. Chargoff demonstrated that the concentrations of adenine in DNA are equal to that of thymine, and concentrations of cytosine are equal to guanine. With this information, Watson and Crick were able to determine that the bonding of adenine to thymine A-T and cytosine to guanine C-G form the steps of the twisted-staircase shape of DNA.

The sugar-phosphate backbone forms the sides of the staircase. Actively scan device characteristics for identification. Use precise geolocation data. Select personalised content. Create a personalised content profile. Measure ad performance. Select basic ads. Create a personalised ads profile. Select personalised ads. Apply market research to generate audience insights. Measure content performance. Develop and improve products. List of Partners vendors. You can't stare at the double helix for very long without having a sense of awe about the elegance of this information molecule DNA, with its double helical form basically being the way in which all living forms are connected to each other, because they all use this same structure for conveying that information.

Of course, this is Watson and Crick's incredible realization back in , but it will stand in history as probably one of the most significant scientific moments of all time. Francis S.

Two hydrogen bonds connect T to A; three hydrogen bonds connect G to C. The bottom four base pairs are shown flattened instead of twisted, so this region can be easily seen in a cut-away showing a close-up view. The cut-away shows the individual atoms and bonds in the DNA molecule. Phosphate groups are depicted within light brown spheres, and the bonds between the phosphate and oxygen atoms are shown. The sugars are represented by grey pentagons that show where oxygen atoms and hydrogen atoms are attached to the unmarked carbon atoms at the corners.

An oxygen atom from each phosphate molecule is connected by a black line to a carbon atom from the sugar molecule. These black lines represent the covalent bonds between the sugars and phosphate groups. The sugar molecules are each attached to a nitrogenous base. The nitrogenous bases from the two DNA strands meet in the center of the molecule, where they are connected with hydrogen bonds shown by dotted, red lines. At the top left side, a guanine base with two fused rings G, shown in blue is bound to a cytosine base with a single ring C, shown in gold on the opposite strand.

These two bases are held together by three hydrogen bonds. Below this base pair, a thymine base with a single ring T, shown in red is bound to an adenine base with two fused rings A, shown in green on the opposite strand.

These two bases are held together by two hydrogen bonds. Below this pair, a single-ringed cytosine base is bound to a double-ringed guanine base by three hydrogen bonds. In the final pair, an adenine base with two fused rings is bound to a single-ringed thymine by two hydrogen bonds.

Figure 5: Three different conformations of the DNA double helix. A A-DNA is a short, wide, right-handed helix.

Genetics: A Conceptual Approach , 2nd ed. All rights reserved. References and Recommended Reading Chargaff, E. Preface to a grammar of biology. Science , — Dahm, R. Human Genetics , — Levene, P. Journal of Biological Chemistry 40 , — Rich, A. Nature Reviews Genetics 4 , — link to article Watson, J. Nature , — link to article Wolf, G. Article History Close. Share Cancel. Revoke Cancel. Keywords Keywords for this Article. Save Cancel. Flag Inappropriate The Content is: Objectionable.

Flag Content Cancel. Email your Friend. Submit Cancel. This content is currently under construction. Explore This Subject. Applications in Biotechnology. DNA Replication. Jumping Genes. Discovery of Genetic Material. Gene Copies. No topic rooms are there. Or Browse Visually. Other Topic Rooms Genetics. Student Voices. The double helix is a description of the molecular shape of a double-stranded DNA molecule.

However, a crucial contribution that enabled this discovery was made by Rosalind Franklin, who was not acknowledged at that time. After her death, Crick said that her contribution had been critical. The double helix describes the appearance of double-stranded DNA, which is composed of two linear strands that run opposite to each other, or anti-parallel, and twist together.