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Questions and Answers
Site-specific recombinases facilitate DNA breakage and rejoining by:
Site-specific recombinases facilitate DNA breakage and rejoining by:
- Utilizing ATP hydrolysis to break phosphodiester bonds directly.
- Sequentially cleaving each DNA strand without energy conservation.
- Introducing random mutations at the cleavage site to promote strand exchange.
- Storing the energy of the broken phosphodiester bond through a covalent protein-DNA intermediate. (correct)
How do serine recombinases differ from other types of recombinases in their mechanism of action?
How do serine recombinases differ from other types of recombinases in their mechanism of action?
- They cleave all four DNA strands within the crossover region, resulting in staggered cleavages. (correct)
- They require an RNA intermediate to facilitate strand exchange.
- They introduce single-stranded breaks that are immediately ligated without forming hybrid duplexes.
- They cleave only two DNA strands within the crossover region.
Which of the following is a key characteristic of transposition?
Which of the following is a key characteristic of transposition?
- It exclusively occurs through a conservative, cut-and-paste mechanism without duplication.
- It requires the presence of telomeres at the insertion site.
- It always involves homologous recombination between identical DNA sequences.
- It involves the movement of mobile genetic elements from one DNA site to another. (correct)
What potential consequence can arise from transposon insertions?
What potential consequence can arise from transposon insertions?
Which mechanism do retrotransposons utilize for their movement within the genome?
Which mechanism do retrotransposons utilize for their movement within the genome?
In V(D)J recombination, what is the main function of this process?
In V(D)J recombination, what is the main function of this process?
What is the role of nonhomologous end joining in V(D)J recombination?
What is the role of nonhomologous end joining in V(D)J recombination?
What is a 'cut-and-paste' mechanism in the context of transposition?
What is a 'cut-and-paste' mechanism in the context of transposition?
How does replicative transposition differ from cut-and-paste transposition?
How does replicative transposition differ from cut-and-paste transposition?
Gene rearrangements during antibody production share mechanistic similarities with what other process?
Gene rearrangements during antibody production share mechanistic similarities with what other process?
Flashcards
Site-Specific Recombination
Site-Specific Recombination
Recombination between specific DNA sequences, dependent on site-specific recombinases.
Site-Specific Recombinases
Site-Specific Recombinases
Enzymes that recognize and bind specific DNA sequences to facilitate DNA breakage and rejoining.
Transposition
Transposition
Genetic recombination where mobile genetic elements move from one DNA site to another.
Transposable Elements (Transposons)
Transposable Elements (Transposons)
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Cut-and-Paste Transposition
Cut-and-Paste Transposition
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Replicative Transposition
Replicative Transposition
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V(D)J Recombination
V(D)J Recombination
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Serine Recombinases
Serine Recombinases
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Retrotransposons
Retrotransposons
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Study Notes
- Specialized recombination leads to new arrangements of DNA sequences.
Site-Specific Recombination
- Occurs between specific DNA sequences and depends on site-specific recombinases.
- Site-specific recombinases recognize and bind particular DNA sequences
- Recombinases facilitate the breakage and rejoining of DNA strands.
- The energy of the broken phosphodiester bond is stored through a covalent protein-DNA intermediate.
- An example of site-specific recombination is the inversion of a DNA segment carrying genes A and B
- Serine recombinases cleave all four DNA strands within the crossover region.
- Staggered cleavages from serine recombinases lead to a hybrid duplex in recombinant products.
- Examples include the Cre-lox system of bacteriophage P1 and the FLP recombinase of yeast.
- Gene rearrangements for antibody production in vertebrates (V(D)J recombination) occur at specific sites.
- V(D)J recombination shares mechanistic similarities with transposition.
Transposition
- Mobile genetic elements (transposable elements or transposons) move from one DNA site to another.
- Movement occurs via recombination between sequences at the ends of the transposable element and a host cell DNA sequence.
- Movement can happen with or without duplication of the element.
- In some instances, the recombination involves a transient RNA intermediate.
- The transposon excises from one DNA site and inserts into another, potentially leading to short repeated sequences at the new target site (cut and paste mechanism).
- Replicative transposition involves DNA replication and can lead to two copies of the transposon.
- Transposon insertions can cause mutations and genome instability, particularly in plants.
- Retrotransposons use reverse transcriptase for their movement.
Examples of Transposons
- Recurring themes feature in the regulation of some well-understood transposons and transposon families.
V(D)J Recombination
- V(D)J Recombination involves the assembly of gene segments to encode proteins for the vertebrate immune system.
- This process can fuse DNA between V and J segments.
- Nonhomologous end joining repairs double-stranded DNA breaks after hairpin hydrolysis in the V(D)J recombination pathway.
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