Replication and repair Flashcards
(18 cards)
What are the main processes in the flow of genetic information?
- Replication (DNA Synthesis)
- Transcription (RNA Synthesis)
- Translation (Protein Synthesis)
Each process plays a critical role in the expression and replication of genetic information.
What enzyme is responsible for the separation of DNA strands during replication?
Helicase
Helicase unwinds the DNA double helix, creating a replication fork.
What is the function of primase in DNA replication?
Starts the process by making a small piece of RNA called primer
The primer serves as the starting point for the synthesis of the new DNA strand.
What direction does DNA polymerase add DNA bases?
5’ to 3’ direction
DNA polymerase can only add nucleotides to the growing strand at the 3’ end.
What is the role of exonuclease in DNA replication?
Removes all RNA primers from both strands of DNA
Exonuclease ensures that the primer is eliminated before the finalization of the DNA strands.
What enzyme seals up the fragments in DNA replication?
DNA ligase
DNA ligase forms covalent bonds between adjacent nucleotides, creating a continuous DNA strand.
Why is DNA replication described as semi-conservative?
Each DNA molecule is made up of one old (conserved) and one new strand
This method of replication ensures genetic continuity.
What is the function of DNA gyrase?
Introduces negative supercoils ahead of the replication fork
DNA gyrase is a topoisomerase II that helps relieve torsional strain during DNA replication.
What is a virus?
A microscopic infectious agent that can replicate only inside living cells
Viruses require a host cell to reproduce and carry out their life cycle.
What are the main components of a virus?
- Genetic Material: DNA or RNA
- Capsid: Protein shell
- Envelope (optional): Lipid envelope derived from the host cell
The structure of a virus is critical for its ability to infect host cells.
What is the initial error rate of DNA polymerase during replication?
1 in 10,000 base pairing errors
This error rate is significantly reduced by proofreading mechanisms.
What is the new error rate for DNA that has been proofread?
1 in 1 billion base pairing errors
Proofreading enzymes greatly enhance the accuracy of DNA replication.
What factors influence the rate of spontaneous mutations?
- Accuracy of DNA replication machinery
- Efficiency of DNA repair mechanisms
- Exposure to mutagenic agents
These factors can affect the stability of the genome.
What are induced mutations?
Mutations resulting from exposure to mutagens
Mutagens are physical and chemical agents that cause changes in DNA.
What are the two main causes of genome evolution?
- Damage
- Copy errors during replication
These factors contribute to nucleotide substitutions in genomes.
Why is the repair mechanism important in DNA replication?
Damage to this system increases the likelihood of getting cancer
Efficient DNA repair is crucial for maintaining genomic integrity.
In which gender is the rate of mutagenesis higher, and why?
Higher in males due to more cell divisions in the male germline
This leads to higher mutation rates on the Y chromosome compared to the X chromosome.
What is the relative rate of transitions compared to transversions in mammals?
Rate of transitions is about twice as high as transversions
Transitions involve changes between similar types of bases, while transversions involve changes between different types.
