Assignment # 5: DNA Replication and Protein Synthesis.

Assignment # 5: DNA Replication and Proteing Synthesis

1. Why is DNA synthesis said to be "semiconservative"?

Answer: DNA synthesis is said to be "semiconservative" because each new double-stranded DNA contains one old strand 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?

Answer: DNA polymerase plays a role in DNA replication because it is an enzyme that catalyzes the covalent bond between the phosphate of one nucleotide and the deoxyribose of the next nucleotide. DNA polymerase also forms the coplementary DNA strand in the 5' to 3' direction. DNA primase plays a role because it is the enzyme that catalyzes the formation of RNA starting segment. Helicase is the enzyme that breaks H-bonds. Topoisomerase unwinds DNA and DNA ligase catalyzes the connection of two Okazaki fragments.

3. What is the difference between how the leading strand and the lagging starand are copied during DNA replication? Why do they have to be synthesized differently in this fashion?

Answer: The difference between the leading strand and the lagging strand are that the leading strand's DNA primase creates a single RNA primer to start the replication while the lagging strand's DNA primase creates RNA primers in spaced intervals. Another difference is that the lagging starand matches the Okazaki fragments in the 5' to 3' direction while the leading strand just synthesizes the matching strand. In the leading strand the DNA ligase connects the fragment at the starts of the new strand to the end of the new strand. With the lagging strand the DNA ligase connects the Okazaki fragments to one another which covalently bonds the phosphate in one nucleotide to the deoxyribose of the ajacent nucleotide. They are synthesized differently because of the okazaki fragment.

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

5. What are the four key differences between DNA polymerase and RNA polymerase? (they are different molecules doesn't count as one!)

Answer: The four key differences:

6. Compare and contrast codons and anticodons?

Answer: For every three mRNA or codon specify an amino acid. example: GACCUAGCC. tRNA have an anticodon region that specifically binds to its codon.

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

Answer: Alternative splicing is when Exons are "coding" regions. Introns are removed, the different combinations of exons form different mRNA which result in multiple proteins from the same gene.

8. During translation what amino acid sequence would the following mRNA segment be conversted into: AUG GAC AUU GAA OCG

Answer: Met, Asp, Lle, Glu, Pro

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?

Answer: Prokaryotes can both transcribe and translate a gene at the same time because they occur simultaneously in the cytoplasm. Eukaryotes cannot because transcription occurs in the nucleus and translation occurs in the cytoplasm.