Topic 2 Molecular Biology Review
**Review all the “understanding” statements at the beginning of each section.
Key facts
2.6
44. A DNA nucleotide contains a sugar (deoxyribose), a nitrogenous base (adenine, thymine, cytosine, or
guanine), and a phosphate group. Nucleotides are the building blocks of DNA.
45. Nucleotides are bonded to one another when the phosphate of one nucleotide forms a covalent bond with the
C3 of the other nucleotide.
46. DNA molecules consist of two strands of nucleotides linked together to form a double helix. Hydrogen
bonds between the bases of the two strands allow the linkage. Adenine will only pair with thymine and cytosine
will only pair with guanine. This is called complementary base pairing.
2.6 DNA STRUCTURE
**What does DNA stand for?
**What is its function?
**What are the sub-units of DNA?
**The sub-units are composed of a ___________, phosphate and a_________
**The sugar in DNA is______________.
**The four bases found in DNA are:
**DNA is in the shape of a___________ ____________
**Describe what is found on the sides of the “ladder” and the type of bond found there
**Describe where the bases are found on a DNA molecule
**Distinguish between a purine and a pyrimidine
**Which bases are purines? Which are pyrimidines?
**Which bases are complementary and how many hydrogen bonds are located between them?
**A purine always pairs with a ________________.
**Where is DNA located in the cell? Approximately how long is it?
**How does DNA fit into the nucleus?
**Describe the structure of a nucleosome
**What does it mean when we say DNA is “anti-parallel”?
**What 2 men received the Nobel prize for DNA’s discovery? What person got the short end of the stick?
2. Draw and label a sample diagram of the molecular structure of DNA. A simple diagram is sufficient as long
as A-T and C-G hydrogen bonds are properly shown with the sugar-phosphate backbones.
34. What are the three parts of a nucleotide?
35. What are the four possible bases in DNA?
36. Explain where one would find covalent bonds in a single strand of DNA.
36. Explain where one would find hydrogen bonds in a double-stranded molecule of DNA.
37. What bases always connect by complementary base-pairing in DNA?