What does this diagram represent?
This is two different ways to represent DNA. The left-hand diagram is called a space-filling model.
In the right-hand diagram, what do the light blue and light red shapes represent? What are the letters for? Why are there two shapes?
These are called bases. There are 4 bases: adenine, guanine, cytosine, and thymine, represented by the 4 letters. The two different shapes represent the two classes of bases. Adenine and guanine are both pyrimidines and cytosine and thymine are both purines.
What do the solid lines and dotted lines in the right-hand diagram represent?
The solid lines are covalent bonds, which are the strongest bonds in the molecule. The dotted lines are hydrogen bonds, which are weaker. Drawing a curve down the middle of the molecule through the hydrogen bonds would show where the two halves of the molecule would split apart.
What do the C, H, O, P and N represent?
These are the 5 elements that make up DNA: carbon, hydrogen, oxygen, phosphorus and nitrogen. All of the nitrogen atoms are found on the bases, which is why they are sometimes referred to as nitrogenous bases. The phosphorus atoms are all found in vertical lines on the outside of the molecule. This is known as the phosphorus backbone.
What do the pentagons with a O in them represent in the right-hand diagram?
The pentagons are part of a deoxyribose molecule, a 5-carbon sugar. The pentagon represents 4 of those carbons, because the fifth corner of the pentagon is formed by an oxygen atom. The fifth carbon is also shown, attached to the pentagon but not part of the pentagon.
What does 3′ and 5′ represent in this diagram?
The carbons in the deoxyribose are counted counterclockwise starting at the oxygen atom. The first carbon is attached to the base in the center. The third and fifth carbons are attached to a phosphate group. The 3′ and the 5′ at the top and bottom of the diagram represent the orientation of each strand of DNA which run in opposite directions.
What do the white arrows represent in the left-hand diagram?
These arrows represent the direction that DNA is replicated, which is always from the 5′ end to the 3′ end.
What does “major groove” and “minor groove” indicate?
The DNA molecule is made of two strands which twist around each other, forming a double helix. These two strands are separated by grooves which are not symmetric. The major groove is where the separation is larger and the minor groove is where the separation is smaller.
CoMo Science 
Leave a comment