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#genetic transfer

8 public questions tagged with this topic.

Plant tissue culture 2

Somatic hybridization can transfer:

Somatic hybridization can transfer extensive genetic material ranging from blocks of linked genes to entire chromosomes or whole genomes, contrasting with single gene transformation using plasmid vectors. When two protoplasts fuse, initial heterokaryon contains cytoplasm of both parents and nuclei that may fuse producing allotetraploid somatic hybrid carrying full complement of chromosomes from both species, allowing introgression of polygenic quantitative trait loci QTL controlled by multiple genes interacting for disease resistance, abiotic stress tolerance, quality attributes that cannot be

Ref: Helgeson 1979 potato somatic hybrid; Bhat & Bhat 2011 gene blocks transfer.

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Microbial genetics

Co-transformation is useful for

Co-transformation detects simultaneous uptake and integration of two markers from same donor fragment, indicating they reside within length of transforming DNA. By scoring frequency of double transformants versus single, geneticists estimate proximity and linear order of three factors using two-point and three-point crosses. Higher co-transformation implies shorter separation. Beadle-Tatum era used auxotrophic markers to construct first bacterial maps before conjugation mapping. Because transformation does not require cell contact, it allows mapping closely linked genes that interrupted mating

Ref: Hartl & Ruvolo, Genetics, 6th ed., Chapter 6: Gene Mapping by Cotransformation; NCBI Bookshelf

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Microbial genetics

Conjugation requires

Conjugation requires physical cell-to-cell contact established by sex pilus encoded by tra operon of conjugative plasmid. Donor F+ extends pilus, attaches to recipient F- surface receptor, retracts to bring cells close, and forms conjugative junction or mating bridge. Type IV secretion system then transfers single-stranded plasmid DNA in 5' to 3' direction, with rolling circle replication replacing donor strand. Chemical or enzymatic treatment that prevents pairing abolishes transfer. Experimental interrupted mating exploits contact dependence to map gene order by timing of marker entry into r

Ref: Hartl & Jones, Genetics, 8th ed., Chapter 6: Bacterial Conjugation Requirements; Wollman & Jacob

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Microbial genetics

Transduction is mediated by

Transduction was discovered by Zinder and Lederberg in Salmonella as gene transfer mediated by bacteriophages. During lytic cycle, phage enzymes mistakenly package host chromosomal DNA into capsid instead of phage genome, creating transducing particle. Upon infection of new cell, bacterial DNA injects and recombines. Generalized transduction packages random host fragments due to pac site errors; specialized transduction arises when prophage excises imprecisely bringing adjacent bacterial genes. Both depend on phage as vector, distinguishing transduction from naked DNA transformation or contact

Ref: Griffiths et al., Introduction to Genetic Analysis, 12th ed., Chapter 6: Transduction Mechanisms; Nature Scitable

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Microbial genetics

DNAse treatment inhibits which process?

DNase I hydrolyzes phosphodiester bonds in extracellular DNA, fragmenting it to oligonucleotides unable to transform cells. Transformation dependence on intact naked DNA makes it uniquely sensitive to DNase treatment, while conjugation requires pilus contact and protected single-strand transfer through secretion channel, and transduction packages DNA inside phage capsid shielding it from nuclease. Lederberg and Tatum used DNase resistance to distinguish conjugation from transformation. Experimentally, loss of recombinant formation after DNase addition confirms transformation mechanism versus o

Ref: Hartl & Jones, Genetics, 8th ed., Chapter 6: DNase Test for Transformation; Avery et al., 1944

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Microbial genetics

Horizontal gene transfer does NOT include

Horizontal gene transfer comprises mechanisms that move DNA between non-parental cells within same generation: transformation uptake of naked DNA, transduction via bacteriophage accidental packaging, and conjugation via direct cell contact and plasmid transfer. Binary fission is not horizontal; it is vertical replication producing daughter cells. Transformation, transduction, and conjugation increase genetic diversity, spread antibiotic resistance, and allow mosaic genomes. Distinguishing horizontal from vertical mechanisms is crucial for tracing gene flow, mapping mobile elements, and underst

Ref: Nature Reviews Microbiology, Horizontal Gene Transfer Mechanisms; Hartl, Chapter 6

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Microbial genetics

F plasmid is involved in

F plasmid, or fertility factor, is 100 kb conjugative plasmid carrying tra operon encoding sex pili, type IV secretion system, and regulation of cell contact. Cells harboring F express F pili, act as donors F+ and initiate conjugation by transferring single-stranded copy of plasmid to F- recipient via pilus. F also integrates rarely to form Hfr. Its role is horizontal transmission of itself and mobilization of other DNAs, spreading genes like antibiotic resistance. Classic Lederberg-Tatum experiments used F to demonstrate bacterial recombination, revolutionizing prokaryotic genetics analysis.

Ref: NCBI Bookshelf, F Factor and Conjugation; Griffiths et al., Chapter 6: Bacterial Mating

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