Name: _____________________________________________________ Date:______________


Structure of DNA and RNA

Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are two of the cellís most important molecules. These nucleic acids have a complex three-dimensional structure that enables them to direct protein synthesis in the cell.

Study the structure of the DNA and RNA molecules shown below. Fill in the missing labels. Then complete the chart and answer the questions.


Type of Sugar

Types of nitrogen bases

Number of nucleotide strands












1.      The two DNA strands twist around each other. The is best described as a ___________________



2.       The repeating units of _____________________________ and ___________________________ make the backbone of DNA and RNA.


3.      In a DNA molecule, the nitrogen bases of one strand attach to the nitrogen bases of the other by following  _____________________________________ rule. The bases are held together by




4.      A strand of DNA contains the following bases A-T-C-G-A-C-T. What will be the bases on the complementary DNA strand? ______________________________________.What will be the


bases on the complementary RNA strand? _________________________________________


5.      Part of the DNA molecule shown above is starting to unwind. What two cellular activities could this be the start of? _____________________________________________________________

Carefully read each term or phrase in the left-hand column of the following table. If the term or phrase applies to DNA, place a check mark in the column labeled DNA. If it applies to RNA, place a; check mark in the column labeled RNA.I f it applies to both nucleic acids, place a check mark in both columns.












Double Helix



Deoxyribose as the sugar



Made during replication




Ribose as the sugar



Made during transcription







Exact copy







Acts as a messenger




Has nitrogenous bases



More than one form







Found in the nucleus







Leaves the nucleus




Template for synthesis of nucleic acids



Does not leave the nucleus