How to Understand DNA Structure

Understanding the structure of DNA from a diagram requires a little imagination. Otherwise, diagrams of DNA would all resemble oozing gelatinous goop---which is how it actually appears to the naked eye. The "structure" of DNA refers to its molecular make-up. To understand that structure, just keep the following steps in mind.

Things You'll Need

• Diagram of DNA strand

Instructions

1. Understand the solid lines. DNA is composed of two strands made up of deoxyribose, sugar and a phosphate. These strands are called the "backbone." The backbone doesn't hold any actual genetic information---its sole purpose is to hold up the strand. The two strands are antiparallel, or flipped with respect to one another.

2. Understand the letters. Sugar molecules connect nitrogenous bases (the molecular chemicals that make up genetic information) to the backbone. The nitrogenous bases are A, C, G, T, or adenine, cytosine, guanine and thymine. Each DNA molecule has a different order of these four molecules. For example, one DNA will be CGTACGCTA and another CATAGCTTCA. The nitrogenous bases, sugar, and phosphate together are called the "nucleotide."

3. Understand "base pairing." This involves knowing the "base pairing rule": A always bonds with T, forming one base pair; likewise, G always bonds with C, with no exceptions, forming another base pair. Therefore, a CGTACGCTA nucleotide on one strand would be, on the other, antiparallel, strand, GCATGCGAT.

4. Understand the dotted lines. Hydrogen bonds, which hold base pairs together, are weaker than most chemical bonds and break easily. That's why diagrams of DNA use dotted lines to represent the hydrogen bonds between base pairs.

References

• DNA Structure, Synthesis, and Fingerprinting
• DNA---Structure

Resources

• University of Illinois