Korean, Edit

Chapter 5-1. Horizontal transfer of genes

Higher category : 【Biology】 Chapter 5. Cell Division and Cancer 

1. Virus

2. Bacterial recombination

3. Mobility DNA

1. Virus

2. Bacterial recombination

⑴ How to Introduce External DNA into Cells

① Transformation : CaCl₂ transformation, etc.

② Transduction : How DNA is injected into cell lines through viruses such as phage

③ Transfection : Injecting DNA Directly into Cell Lines

④ Conjugation

⑤ Electroporation

⑥ Microinjection

⑦ Gene gun

⑧ Protoplast formation : Yeast, Plant Cell Protoplast

⑵ Transformation : The process of changing the genotype and phenotype of a bacterium by taking in DNA from another individual from the outside environment

① Experimenter should make competent cell which is easy to bind microorganism with DNA

② Gene Mapping Through Transformation : At the same time, the closer you are to trigger a transformation,

⑶ Transduction : The process by which bacteriophages transfer genes from one host bacterium to another

See. Generally toxic phage, in certain cases moderate phage

① 1^st. Phage will infect some bacteria. This bacterium becomes a donor cell

② 2^nd. Phage DNA is replicated, and cells synthesize large quantities of proteins encoding from phage genes

○ Phage protein prevents the synthesis of proteins encoded by the host cell

○ DNA of host cell is cut off

③ 3^rd. When new phage particles are assembled, bacterial DNA fragments containing specific alleles may be packaged in the phage capsid.

④ 4^th. When the phage carrying the allele infects the receptor bacteria, recombination occurs between the donor and recipient cells. This process is a homologous recombination similar to the crossover phenomenon.

⑤ 5^th. As a result, the genotype of the recombinant cell may be different from that of the donor or the receptor.

⑥ Genetic maps can be created by transduction

⑷ Join : Direct transfer of genetic material between two adjacent bacteria

① F plasmid

○ F plasmid : Consists of 25 genes, most of which are needed for sexually transmitted mothers

○ Donor cell (F⁺) if bearing F plasmid, otherwise receptor cell (F^-)

○ F⁺ delivers F plasmid to F^- to form F⁺

② Common Donor Strain Conjugation : Genetic transfer through the gonadotum from donor cells to receptor cells

○ 1^st. F⁺ cells form a junction with F^- cells and one strand of plasmid is broken

○ Conditions of Receptor Cells : rec+

○ 2^nd. Using unbroken strands as templates, cells form new strands

○ 3^rd. In the meantime, the broken strands come off and one end enters the F- cell.

○ 4^th. Plasmids are circularly linked in receptor cells

○ 5^th. Receptor cells also become F+ cells

○ Junction pathways fall off before the entire chromosome and the remaining F factor are fully delivered

See. When the receptor cell holds some of the DNA of the donor cell

○ F plasmids are rarely delivered last to become F+ cells

○ Disadvantages : Extremely low frequency

③ High Frequency Recombinant Strain Conjugation

○ High Frequency Recombination (Hfr) Donor Cells : Strain with F Factor Inserted into Chromosome DNA (Bac)

○ F plasmid randomly inserted into the genome

○ Solve the low frequency problem of F⁺-F^- junctions

○ Passing F-plasmid and Chromosome Particles → DNA Recombination in Bacteria

○ The F factor is passed last; Rotational direction of rotation (clock, counterclockwise) depends on the relative position

④ Interrupted mating technique : Application in Genetic Mapping

○ 1^st. Hfr strain is strs leu⁺ thr⁺ azi^r ton^r lac⁺ gal⁺ 

○ Condition : Antibiotic Sensitivity, No Nutrition

○ 2^nd. F-strain is strr leu^- thr^- azi^s ton^s lac^- gal^-

○ Condition : Antibiotic Resistance, Nutritional Requirements

○ 3^rd. Cultured in medium with streptomycin but without threonine and leucine : Only the strains with str^r leu⁺ thr⁺ survive

○ 4^th. azi^r survives an additional 8 minutes after splicing : azi^r next to str^r leu⁺ thr⁺

○ 5^th. ton^s survives 10 minutes after splicing : tons next to strr leu+ thr⁺ azi^r 

○ 6^th. additional lac⁺ survives 16 minutes after splicing : lac⁺ next to str^r leu⁺ thr⁺ azi^r ton^s

○ 7^th. An additional gal+ survives 25 minutes after splicing : gal⁺ next to str^r leu⁺ thr⁺ azi^r ton^s lac⁺

3. Mobility DNA

⑴ Summary

① Mobile DNA contains transposons and retrotranspozones

○ Transposon : Cut and paste

○ Retrotransposon : Copy and paste

② Movable DNA can be mutagenic

⑵ Composition of transposon

① Insertion sequence is located at both ends. Antibiotic resistance gene may be located in the center

② Potential factor : DNA that moves substantially

③ Insertion sequence : 2500 base pairs or less. Consists of two parts

○ Transposase : Catalyzing the insertion of genes elsewhere

○ Reverse iteration sequence : Sequences at both ends of the transposon. Same as each other but in opposite direction. 20-40 nucleotides

⑶ McClintock’s research

① DS is a factor without translocation enzyme gene in Ac

② Ds is transferred by Ac and overlaid on the genetic code of gene C

③ Ac metastasizes itself and overwrites the genetic code at gene C sites

④ The size of the spot on the spotted grain is related to the point at which the dislocation occurred during development.

Input : 2015.7.12 00:08