Name: Date: Period:
Study the figure below. It illustrates the shape of the DNA molecule. DNA is a double helix. The two helices of the DNA molecule form what is often referred to as a “twisted ladder.” The sides of the ladder are made up of alternating sugar molecules and phosphate groups. The sugar is a 5-carbon deoxyribose sugar. Each phosphate group is a phosphate atom with 4 oxygen atoms bonded to it. Each “rung” of the DNA ladder is made up of two nitrogen bases. Nitrogen bases are organic compounds containing the element nitrogen. Together, a sugar, a phosphate group, and a base make up a nucleotide. A nucleotide is the basic unit of DNA.
Nitrogen bases are grouped into two classes: the purines and the pyrimidines. The purines are adenine (A) and guanine (G). The pyrimidines are cytosine (C) and thymine (T). In a DNA molecule, a purine bonds to a pyrimidine to make up each rung of the ladder. Adenine bonds only with thymine. Cytosine bonds only with guanine.
Make a key that includes all of the parts of the DNA molecule. Color the diagram above using your chosen colors to accurately show the structure of the above double helix. (3 pts)
Key:Adenine: / Cytosine: / Sugar:
Thymine: / Guanine: / Phosphate:
Use the information from the 1 st page to color and label the following diagram. (2 pts)
1. (1pt) 2. (1pt)
3. (1pt) 4. (1pt)
5. (1pt) 6. (1pt)
7. (1pt) (hint, it’s composed of a sugar, a phosphate, and a base)
8. What molecules make up the sides of the double helix molecule? (2 pts)
and
9. Which nitrogen bases pair with each other to form the rungs of DNA? (2 pts)
with ; with
10. (1 pt) The acronym DNA stands for ______.
11. (1 pt) DNA makes up chromosomes, which are located in the ______of a cell.
12. (1 pt) Small sections of a DNA molecule that determine genetic traits are called ______.
13. (1 pt) DNA can also be found in the form of ______, which are loose coils or strands of DNA.
2