DNA Structure and Function - Study Guide
1. Summarize the contribution to the understanding of DNA by each of the following scientists: Linus Pauling, Watson and Crick, Maurice Wilkins and Rosalind Franklin.



2. List the three components of a nucleotide. Nucleotides are the building blocks of the DNA and RNA used as genetic material. Nucleotides also are used for cell signaling and to transport energy throughout cells.

The three components of the nucleotide are :
1. Nitrogenous Base: Purines and Pyrimidines are the two categories of nitrogenous bases. Adenine and guanine are purines. Cytosine thymine and uracil are pyrimidines. In DNA, the bases are adenine (A), Thymine (T), Guanine (G), and cytosine (C). In RNA the bases are adenine, thymine, uracil and cytosine
2. Pentose sugar: In DNA, the sugar is 2'-deoxyribose. In RNA, the sugar is ribose. Both ribose and deoxyribose are 5-carbon sugars. The carbons are numbered sequentially, to help keep track of where groups are attached. The only difference between them is that 2' oxyribose has one less oxygen atom attached to the second carbon
3. Phosphate Group: A single phosphate group is PO4 3-. The phosphorous atom is the central atom. One atom of oxygen is connected to the 5 carbon in the sugar and to the phosphorus atom. When phosphate groups link together to form chains as in ATP, the link looks like O-P-O-P-O-P-O, with two additional oxygen atoms attached to each phosphorous, one on either side of the atom. The base is attached to the primary or first a carbon. The number 5 carbon of the sugar is bonded to the phosphate group. A free nucleotide may have one, two or three phosphate groups attached as a chain to the 5 carbon of the sugar. When nucleotides connect to form DNA or RNA the phosphate of one nucleotide attached via a phosphodiester bond to the 3 carbon of the sugar of the next nucleotide, forming the sugar phosphate backbone of the nucleic acid.


3. List the nitrogen bases found in DNA. The nitrogenous bases are adenine (A), guanine(G), cytosine(C), thymine(T), and uracil(U). Adenine and guanine are purines (contains a six membered ring of carbon and nitrogen fused to a five membered ring). Adenine and guanine are both found in DNA and RNA.


4. Label and describe the parts of the nucleotide:


5. What links the nucleotides together to form the strand of DNA? Describe the type of bond and the enzyme responsible for linking the nucleotides.

6. Explain the term complimentary base pairing.


7. Explain the significance of the base-pairing pattern.

8. Explain why the two strands of DNA are said to be antiparallel.

9. Explain the process of DNA replication.


10. Explain why DNA replication is said to be semiconservative.

11. Predict the alternative base pairing for a given nucleotide sequence like ATTGCCTGAACCTCG.


12. Describe the action of DNA polymerase and DNA ligase in DNA proofreading and repair.

13. Label this diagram of DNA replication:



14. How does DNA differ from RNA?

15. In your own words, explain how information is transferred from a gene to a protein.


16. What is the difference between transcription and translation?

17. Explain the role of RNA polymerase in transcription.

18. Describe the structure of tRNA and explain how that structure is related to its function.


19. Explain the structure of a ribosome and explain how its structure is related to its function.

20. Describe how mRNA is processed before it leaves the nucleus.


21. Transcribe the following DNA strand into mRNA and translate that strand into a polypeptide chain, identifying the codons and amino acid sequence.

a. DNA: A T A C G A A A T C G C G A T C G C G G C G A T T C G G
mRNA:
Codons:
Amino Acids:

b. DNA: T T T A C G G C C A T C A G G C A A T A C T G G
mRNA:
Codons:
Amino Acids:

c. DNA: T A C G G G C C T A T A C G C T A C T A C T CA T G G A T C G G
mRNA:
Codons:
Amino Acids:

d. DNA: G T A C G C G T A T A C C G A C A T T C
mRNA:
Codons:
Amino Acids:

22. Define the term mutagen.

23. Describe the concept of junk DNA and its importance in the human genome.


24. Explain why all genes are not expressed in all cells.

25. Describe how a cancer cell is different from a regular cell. Cancer cells mutate and reproduce more quickly than regular cells.


26. Explain the connection between genes and cancer.