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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?
1. 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 is the effect of telomere shortening?
Telomere shortening leads to the eventual cessation of cell division and contributes to aging.
What happens if Helicase is inhibited?
If Helicase is inhibited, the DNA double helix cannot unwind, preventing DNA replication.
What happens if DNA Polymerase III makes an error and it is not corrected?
If DNA Polymerase III makes an error and it is not corrected, it results in a mutation in the newly synthesized DNA strand.
What is the effect of the 5' to 3' directionality of DNA polymerase on the lagging strand?
The 5' to 3' directionality of DNA polymerase causes the lagging strand to be synthesized discontinuously in Okazaki fragments.
What is the consequence of not having single-strand binding proteins?
Without single-strand binding proteins, the separated DNA strands would re-anneal or form secondary structures, hindering replication.
What happens if ligase is non-functional?
If ligase is non-functional, Okazaki fragments on the lagging strand will not be joined, resulting in fragmented DNA.