DNA:  The Molecule of Heredity KEY

Original Document: DNA: The Molecule of Heredity

1. A nucleotide is made of three parts: a _____phosphate______ group, a five carbon _____sugar________, and a nitrogen containing ____base_

2. In a single strand of DNA, the phosphate group binds to the _____deoxyribose (sugar)_______ of the next group.

3. The 5’ end of a single DNA strand contains a free ___phosphate____, while the 3’ end contains a free _______sugar____________.

4. Chromosomes consist of what two substances:  ___DNA_____  &  _____protein____________

5.  DNA was not thought to be the genetic blueprint originally; instead many scientists hypothesized that ____proteins_____ contained the genetic code and blueprint of life.  (They were later proven wrong.)

6. Purines have ____2_____ rings, and pyrimidines have  _____1______ ring.

7. Check each of the following statements that are true with regard to Griffith’s experiments.

a. __X__  Griffith discovered transformation in bacteria.
b. ______ Mice injected with non-encapsulated bacteria quickly became sick and died.
c. ______ Encapsulated bacteria can become “naked” bacteria.
d. ____X__ Bacteria that are naked tend to be harmless.
e. ___X___ Naked bacteria can develop a capsule only after exposure to the DNA of encapsulated bacteria.
f. ______ Griffith’s transforming factor was the protein in the capsule.
g. ______ Heating the encapsulated bacteria preventing transformation of the naked variety.
h. ___X___ Transformation allows bacteria to acquire new genes.
i.  ___X___ Enzymes that destroyed DNA would prevent transformation.

8. Check each of the following statements that are true with regard to the Hershey-Chase experiment.

a. __X___ DNA was labeled with radioactive phosphorous.
b. _______ Protein was not labeled.
c. _______ Radioactive sulfur was found in the offspring phages after they emerged from the cell.
d. ___X___ Phage proteins were not transmitted to host cell or to offspring.

9. Chargaff’s rule states that the DNA of any species contains equal amounts of ________A_______ & _____T_____  and also equal amounts of  _______G_______ &  ________C__________

10. Wilkins and Franklin studied the structure of DNA using  _______X Rays_________  and determined that the shape of the molecule was a ______helix____

11. James Watson and Francis Crick amended Franklin and Wilkins’s conclusions and determined that the shape of the molecule was instead a __double helix ___

12.  In DNA, thymine is complementary to ______adenine________ ; cytosine is complementary to _____guanine______

13. In a strand of DNA, the percentage of thymine is 30 %.  What is the percentage of cytosine in the same DNA strand?  _____20_____

14. Number the steps of DNA replication in the correct order (1, 2, 3)

___2___Polymerase travels down the DNA parent strand from the 3’ to 5’ direction.
___1___  DNA unwinds
___3__  Ligase binds okazaki fragments together

15. Why is DNA replication called “semi-conservative”? _____half of the old stand is saved_____________

16.  What enzyme unwinds or unzips the parent strand?  __helicase______

17. The junction between separated strands is called the _____replication fork_________________

18. What enzyme synthesizes the new DNA strand?  _____DNA polymerase____________

19.  What enzyme binds fragments of DNA on the lagging strand?  _____ligase__________

DNA20.  DNA polymerase only travels in the  ____5____   to  ___3______  direction.

21.  On the diagram:

Label the 3’ and 5’ ends. - look for the free phosphate (black circle)

Circle a nucleotide. three things, phosphate, sugar and base

Label the sugar and phosphate. - 5 sided, phosphate is circular

Label the bases that are not already labeled A - T, G - C


22. The two sides of the DNA helix are held together by ___hydrogen bonds_____________

23. Write out the complete name for DNA: _deoxyribonucleic acid______


24. Name the scientist(s) responsible for each of the following discoveries.

___________Griffith_______________  Bacterial transformation
____________Chargaff____________________ The base-pair rule
_________Avery_____________________ DNA was the hereditary material of viruses
_________Wilkins & Franklin_________________________ The shape of DNA was a helix
__________Watson & Crick______________________ The shape of DNA was a double helix

25. A permanent change in the sequence of bases is called a(n):  _________mutation________________
What  process can prevent these errors from occurring?  _________proofreading____________________