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#deletion

2 public questions tagged with this topic.

Recombination

Orientation of loxP sites in same direction leads to

Outcome of Cre-loxP recombination is dictated by relative orientation and location of loxP sites. When two loxP sites flank a DNA segment on same chromosome in direct repeat orientation, Cre-mediated synapsis brings sites together in parallel alignment, reciprocal exchange excises intervening DNA as circular product bearing one loxP and leaves single loxP at chromosomal locus. This deletion reaction is widely used for conditional knockouts using floxed alleles. Excision is essentially irreversible in absence of reintroduction, especially when circular product lacks replication origin and is lo

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 8: Cre-loxP Deletion by Directly Repeated Sites

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Gene Tar getting

What kind of mutation is produced if one allele has a nucleotide addition and the other a deletion?

CRISPR editing of diploid mammalian cells can affect zero, one or both alleles. When Cas9 induces double strand breaks independently repaired by non-homologous end joining, distinct indel signatures arise per allele. If one chromosome acquires a single base insertion causing frameshift and homologous chromosome acquires base deletion at same locus, alleles carry different mutations yet both disrupted. This state is termed biallelic heterozygous or compound heterozygous mutant, differing from homozygous where both alleles share identical alteration and monoallelic where only one allele mutated.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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