RNA Primer Removal in Bacteria
During DNA replication in bacteria, short RNA sequences called primers are initially synthesized to start the DNA synthesis process. These RNA primers must be removed and replaced with DNA.
Role of DNA Polymerase I
DNA polymerase I is the primary enzyme responsible for removing RNA primers. It possesses two key activities:
- 5' to 3' exonuclease activity: This allows it to remove the RNA nucleotides from the 5' end of the primer.
- 5' to 3' polymerase activity: After removing the RNA, it simultaneously synthesizes DNA to fill the resulting gap.
This process ensures the continuous and accurate replication of the bacterial genome.
Other Enzymes Involved
While other enzymes are crucial for DNA replication, they don't directly remove RNA primers:
- DNA gyrase: Relieves supercoiling stress ahead of the replication fork.
- Primase: Synthesizes the RNA primer, it doesn't remove it.
- DNA polymerase II: Primarily involved in DNA repair.
Therefore, DNA polymerase I is the correct enzyme for RNA primer removal.
Important Questions from Replication Transcription Splicing and Translation
Messenger RNAs (mRNAs) translate to generate polypeptides and the translation terminates at the UGA, UAG or UAA stop codons. The AGA codon acts as additional stop codon in the mitochondria. The longest possible polypeptide(s) that can be hypothetically translated in the cytosol and/or mitochondria, from the given full length mRNA sequence (36 nucleotides) is/are
5'-AACACCAUGACCCAUGUGGCGAGACGGUAGUUAAAA- 3'
- Which of the following statements about initiation of DNA replication in eukaryotes is/are true?
Match the drugs in Group I with their mechanism of action in Group II.
Group I Group II P) Paclitaxel 1) Inhibits protein translation Q) Colchicine 2) Inhibits microtubule depolymerization R) Etoposide 3) Inhibits DNA replication S) Methotrexate 4) Alkylates DNA 5) Inhibits dihydrofolate reductase 6) Inhibits microtubule polymerization Match the enzyme (Column I) with its corresponding function (Column II).
Column I Column II P. Primase 1. RNA dependent RNA synthesis Q. Reverse transcriptase 2. DNA dependent DNA synthesis R. RNA Replicase 3. RNA dependent DNA synthesis S. DNA Polymerase III 4. DNA dependent RNA synthesis Which of the following statements regarding the below mentioned mRNA sequence is/are TRUE?
5`-UGAUGAGCCUUAACCGGGAACGAAUUUAAG-3`
