Download HomeworkCh7

Home work (worth 20 points):Due next week (Thursday)
For Chapter 7 on separate sheets of paper
1. Draw the four nucleotides of DNA
a. label the 5’ and 3’ carbons
2. Draw a chain of connected nucleotides 4-5 long, and the complement strand
in the correct orientation. Show the following important features of DNA:
a. hydrogen bonding that keeps them together
b. 5’ and 3’ end features
3. DNA Replication
a. On prokaryotic chromosomes (or plasmid as well), where is DNA
replication initiated? (replication makes a copy of the DNA during cell
division)
b. What direction does DNA synthesis proceed along the DNA strands?
c. What are the five steps of DNA synthesis? And what enzymes are
involved?
d. How does synthesis proceed on the lagging strand?
4. Draw a cartoon of this process to better understand it. Refer to figure 7.7 in
Chapter 7. In particular, pay attention to the lagging strand. The leading
stand easily continues synthesis, but the lagging strand has to keep adding a
new RNA primer to keep things rolling, then this primer is excised, and DNA
put in its place, and fused to the other DNA. Why?
5. Gene expression
a. What is the role of sigma factors in Bacterial RNA synthesis from DNA.
b. What is the role of transcription factors in Archaea and Eukarya? Hint.
Same as sigma factors in bacteria.
c. What is a promotor?
d. What are the three main phases of RNA synthesis?
e. Can more than one copy of the gene be copied at the same time?
6. Translation
a. What is translation? Why do you think it’s called that?
b. How many different codons are possible for providing a three
nucleotide code for the amino acids? Take a look at Table 7.4
c. Does every amino acid have the same number of codons to match it
during translation? What other codons are there, and what is their
function in protein synthesis?
d. What is the sequence of events that add an amino acid to the growing
polypeptide chain. Be sure to name the enzyms and structures
involved. (Ribosome, t-RNA, startcodon…)