All Flashcards
What is DNA replication?
The process by which cells copy their DNA before dividing, ensuring genetic information is passed on.
What is Helicase?
An enzyme that unwinds the double helix and breaks the hydrogen bonds between the bases during DNA replication.
What is DNA Polymerase III?
An enzyme that adds new DNA nucleotides to the 3' end of the primer, following the template strand during DNA replication. It works in the 5' to 3' direction.
What are Okazaki fragments?
Short fragments of DNA synthesized on the lagging strand during DNA replication.
What are Telomeres?
Protective, non-coding sequences at the ends of chromosomes that shorten over time, contributing to aging.
What is DNA Polymerase I?
An enzyme that removes RNA primers and replaces them with DNA nucleotides during DNA replication. It also proofreads and fixes mistakes.
What are the main steps of DNA replication?
- Unwinding the DNA (Helicase), 2. Preventing supercoiling (Topoisomerase & Single-Strand Binding Proteins), 3. Initiating synthesis with RNA primer (Primase), 4. Adding nucleotides (DNA Polymerase III), 5. Replacing RNA primer with DNA (DNA Polymerase I), 6. Sealing gaps (Ligase).
Describe the role of Helicase in DNA replication.
Helicase unwinds the DNA double helix by breaking hydrogen bonds between base pairs, creating a replication fork.
Describe the function of Primase during DNA replication.
Primase synthesizes a short RNA primer that provides a starting point for DNA polymerase to begin adding nucleotides.
What is the role of Ligase in DNA replication?
Ligase seals the gaps between Okazaki fragments on the lagging strand by forming phosphodiester bonds, creating a continuous DNA strand.
What is the function of Topoisomerase?
Topoisomerase relieves the torsional stress ahead of the replication fork by cutting and rejoining DNA strands, preventing supercoiling.
Describe the function of Single-Strand Binding Proteins.
Single-strand binding proteins bind to single-stranded DNA near the replication fork to prevent strands from re-annealing or forming secondary structures.
What are the key differences between the leading and lagging strands in DNA replication?
Leading Strand: Synthesized continuously in the 5' to 3' direction, following the replication fork. | Lagging Strand: Synthesized discontinuously in the 5' to 3' direction, away from the replication fork, forming Okazaki fragments.
Compare and contrast the functions of DNA Polymerase I and DNA Polymerase III.
DNA Polymerase III: Primarily responsible for adding nucleotides to the growing DNA strand during replication. | DNA Polymerase I: Removes RNA primers and replaces them with DNA nucleotides; also involved in proofreading.
Compare DNA replication in eukaryotes and prokaryotes.
Eukaryotes: Occurs inside the nucleus. | Prokaryotes: Occurs in the cytoplasm.
What is the difference between conservative and semiconservative replication?
Conservative: The original DNA molecule remains intact, and a completely new DNA molecule is synthesized. | Semiconservative: Each new DNA molecule consists of one original strand and one newly synthesized strand.
Differentiate between the roles of primase and ligase.
Primase: Synthesizes short RNA primers to initiate DNA synthesis. | Ligase: Seals the gaps between Okazaki fragments on the lagging strand.