Skip to content
Login Register

#negative selection

3 public questions tagged with this topic.

NATURAL SELECTION

Negative selection refers to

Removal of deleterious alleles reflects key principle in quiz on natural selection, where evolutionary mechanisms shape genetic variation and adaptation. In this context, Removal of deleterious alleles aligns with experimental and theoretical evidence from population genetics, behavioral ecology and molecular phylogeny. Textbooks like Campbell Biology, Futuyma Evolution and Hartl Principles illustrate supporting data. Understanding why Removal of deleterious alleles fits helps integrate natural selection, drift and species concepts essential for NEET, CSIR-NET and GATE examinations. This concept integrates genetics, ecology and molecular evidence, frequently tested in NEET, GATE and CSIR-NET, highlighting links between genotype, phenotype

Ref: Futuyma, Evolution, 4th ed., Chapter 11: Natural Selection.

View Details
Gene Cloning Process

What type of gene is typically used as a reporter in negative selection screening?

Negative selection or insertional inactivation screening uses a reporter gene whose function is lost when foreign DNA integrates within it, allowing differentiation of recombinants from parental vectors. LacZ encoding β-galactosidase serves this purpose efficiently; intact lacZ cleaves X-gal producing blue colonies while insertion disrupts α-peptide coding, yielding white colonies. Origin of replication maintains plasmid copy number, antibiotic resistance gene AmpR provides positive selection, and T7 promoter drives transcription. Among these, only lacZ provides a scorable loss-of-function phenotype suitable as reporter for insertional disruption screening.

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.

View Details
Gene Tar getting

Which gene serves as a negative selection marker in gene targeting experiments?

Positive-negative selection enriches correctly targeted embryonic stem cells for knockout mouse production. The neomycin phosphotransferase gene placed inside homology arms confers G418 resistance, marking any vector integration event. Herpes simplex virus thymidine kinase located outside homology arms provides negative selection. Random integrants retain tk, which phosphorylates ganciclovir into toxic triphosphate nucleotides triggering cell death. Homologous double crossover excludes tk sequences, so true recombinants survive ganciclovir treatment while remaining G418 resistant, eliminating majority of non-specific insertions and ensuring isolation of correctly targeted clones.

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.

View Details