20 Questions
What is the main purpose of DNA replication?
To copy the genetic information required for heredity
Which characteristic of DNA facilitates accurate copying during replication?
Specific base pair hydrogen bonding
What did the Meselson Stahl experiment demonstrate about DNA replication?
DNA replication involves the incorporation of heavier isotopes into nitrogenous bases
During which phase of DNA replication does the helix open out and new DNA strands are produced?
Elongation
What is the starting point of DNA replication in bacteria known as?
Point of origin
What are the phases of DNA replication?
Initiation, Elongation, Termination
Which DNA repair mechanism does not require template information for repair?
Direct Reversals
In which DNA repair mechanism is the error removed as a stretch of nucleotides?
Base Excision Repair (BER)
Which DNA repair mechanism involves only the removal of the affected base?
Mismatch Repair
Which DNA repair mechanism is very similar to nucleotide excision repair but applies only to situations where the 2 different DNA strands contain a mismatch?
Mismatch Repair
Which DNA repair mechanism involves repairing the DNA using sequences from a homologous piece of DNA?
Recombinational Repair
What mechanism involves the binding together of 2 broken DNA ends, which may or may not be the same DNA strands as the original?
Non Homologous End Joining (NHEJ)
Which DNA repair mechanism can repair 2 adjacent T dimers covalently bonded together due to UV light exposure?
Direct Reversals
Which DNA repair mechanism is more error prone as it requires identification of a parental strand?
Mismatch Repair
Which enzyme is responsible for unwinding the DNA helix during replication?
Helicase
What forms when replication bubbles merge and coalesce?
Replication fork
Which enzyme is responsible for synthesizing new DNA strands?
DNA polymerase
What type of replication do eukaryotes exhibit?
Bidirectional replication
What are formed on the lagging strand during DNA replication?
Okazaki fragments
Which enzyme functions by creating RNA sequences complementary to a single-stranded DNA template?
Primase
Study Notes
- DNA replication begins with initiation complex recognizing DNA sequences at the origin, binding, and unwinding the DNA helix
- A replication bubble forms, allowing access to proteins that synthesize new strands
- Replication bubbles merge and coalesce, forming a replication fork, which moves away from the origin in bidirectional replication
- Eukaryotes have multiple origins
- Replication bubble formation creates a template for new DNA strands, which elongate in a 5’ to 3’ direction
- Replication on the opposite strand, known as the lagging strand, is discontinuous
- RNA primers are used to initiate DNA synthesis, with DNA polymerase extending on the 3’ end
- Okazaki fragments are formed on the lagging strand and require processing by DNA ligase
- DNA polymerase is the enzyme responsible for synthesizing new DNA strands, and multiple types exist
- RNA primers are synthesized by primase, which functions by creating RNA sequences complementary to a single-stranded DNA template
- Lags strands are synthesized in short sections, requiring continuous re-initiation and the involvement of multiple enzymes and proteins
- A variety of enzymes and proteins are needed for DNA replication, including helicases, ligases, primases, and polymerases
- Replication proteins and enzymes vary between prokaryotes and eukaryotes
- DNA polymerases have high fidelity and utilize base pairing rules to minimize errors during replication
- DNA gets damaged through endogenous and exogenous sources
- Endogenous sources include replicative errors, oxidative damage, spontaneous alterations, and alkylating agents
- Exogenous sources include UV radiation, carcinogens, radiotherapy, and chemotherapy
- Damage can occur to DNA bases, resulting in oxidation, alkylation, deamination, loss, and dimerization
- DNA backbone can also break, resulting in single or double-stranded breaks and crosslinks
- Damage to DNA is dealt with through the action of various enzymes, such as DNA polymerase, ligase, and helicase, among others.
Learn about the processes of DNA replication and repair in this lecture by Dr. RAJ Radhakrishnan, a lecturer in Biomedical Sciences at St George’s, University of London. Understand the importance of accurate and coordinated DNA replication for heredity, as well as the characteristics of DNA helical structure that affect the process.
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