Assignment 5

1.Why is DNA synthesis said to be “semiconservative”?
DNA is said to be semiconservative because
each new double-stranded DNA contains one old strand (template) and one newly-synthesized
complementary strand.

2. What role do DNA polymerase, DNA primase (a type of RNA polymerase),
helicase, topoisomerase, RNase H, and ligase play in DNA replication?
DNA po;ymerase is an enzyme that catalyzes the covalent bond between the phosphate of one
nucleotide and the deoxyribose (sugar) of the next nucleotide. DNA primase attaches onto the 3’ end of the RNA primer.
Topoisomerase - unwinds DNA
Helicase – enzyme that breaks H-bonds

3. What is the difference between how the leading strand and lagging strand are
copied during DNA replication? Why do they have to be synthesized
differently in this fashion?
In leading strands DNA ligase connects the fragment at the start of the
new strand to the end of the new strand (in circular chromosomes). In lagging strands DNA ligase connects the Okazaki fragments to one another (covalently bonds the
phosphate in one nucleotide to the deoxyribose of the adjacent nucleotide).

4. What would happen if insufficient RNase H were produced by a cell? What if
insufficient ligase were produced by a cell?


5. What are four key differences between DNA polymerase and RNA
polymerase? (“they are difference molecules” doesn’t count as one!)

6. Compare and contrast codons and anticodons?

7. What is alternative splicing? Why is it necessary in eukaryotes?

8. During translation, what amino acid sequence would the following mRNA
segment be converted into: AUGGACAUUGAACCG?

9. How come there are only 20 amino acids when there are 64 different codons?


10. How come prokaryotes can both transcribe and translate a gene at the same
time, but eukaryotes cannot?