DNA replication Flashcards
What is the role of DNA helicase in DNA replication?
DNA helicase separates the two strands of the DNA double helix, allowing each strand to serve as a template for replication.
What is the function of RNA primers in DNA replication?
RNA primers provide a free 3’-OH group that DNA polymerases need to extend the DNA chain. They are synthesized by RNA polymerase and primase
What is the difference between the leading strand and the lagging strand?
The leading strand is synthesized continuously in the 5’ to 3’ direction, while the lagging strand is synthesized discontinuously in Okazaki fragments.
What is the role of DNA ligase in DNA replication?
DNA ligase seals the gaps between Okazaki fragments by joining the fragments together.
What is semiconservative replication?
Semiconservative replication is the process where each of the two daughter DNA molecules consists of one old (parental) strand and one newly synthesized strand
What are the main functions of DNA polymerase I (Pol I)?
Pol I synthesizes DNA by adding nucleotides to the 3’-OH end of the growing DNA chain, has 3’-5’ exonuclease activity for proofreading, and 5’-3’ exonuclease activity to remove RNA primers.
What is the primary role of DNA polymerase III (Pol III) in E. coli?
Pol III is the main enzyme responsible for DNA replication in E. coli, synthesizing the new DNA strand by adding nucleotides in the 5’ to 3’ direction.
What is the error rate of DNA polymerase I?
The error rate of DNA polymerase I is approximately one wrong base per 10 to 100 million nucleotides.
What is the central dogma of biology?
The central dogma describes the flow of genetic information: DNA → RNA → Protein.
What is the role of RNA polymerase in transcription?
RNA polymerase synthesizes RNA from a DNA template during transcription, facilitating template binding, chain initiation, and chain elongation.
What are the main types of RNA polymerase in eukaryotes and their functions?
RNAP I (Pol I): Synthesizes rRNA in the nucleolus.
RNAP II (Pol II): Synthesizes mRNA in the nucleoplasm.
RNAP III (Pol III): Synthesizes tRNA and other small RNAs in the nucleoplasm.
What are the key promoter sequences in prokaryotes?
The key promoter sequences in prokaryotes are TATAAT at the -10 position and TTGACA at the -35 position.
What is the role of aminoacyl-tRNA synthetase in translation?
Aminoacyl-tRNA synthetase attaches the correct amino acid to its corresponding tRNA, ensuring the proper amino acid is incorporated during translation.
What is the function of the ribosome during translation?
The ribosome facilitates the decoding of mRNA, the formation of peptide bonds (transpeptidation), and the translocation of tRNA and mRNA during elongation.
What are the three phases of polypeptide synthesis in translation?
The three phases are chain initiation, chain elongation, and chain termination.
What are the stop codons in the genetic code?
The stop codons are UAA, UAG, and UGA.
Post-Transcriptional and Post-Translational Modifications
What are the main steps in mRNA post-transcriptional processing?
The main steps are capping (addition of 7-methylguanosine to the 5’ end), polyadenylation (addition of a poly(A) tail to the 3’ end), and splicing (removal of introns and joining of exons).
What is the role of RNase III in rRNA processing?
RNase III is involved in the cleavage and processing of rRNA precursors.
What are some common post-translational modifications of proteins?
Common modifications include proteolytic cleavage, acetylation, glycosylation, hydroxylation, and ADP-ribosylation.
What is the genetic code’s degeneracy?
Degeneracy means that multiple codons can code for the same amino acid. For example, leucine is specified by six different codons.
What are the initiating codons in translation?
The initiating codons are AUG (codes for methionine) and GUG (codes for valine, but can also initiate translation).
What are the 21st and 22nd amino acids, and how are they incorporated into proteins?
The 21st amino acid is selenocysteine (Sec), incorporated by the UGA codon, and the 22nd is pyrrolysine (Pyl), incorporated by the UAG codon
