Horizontal Gene Transfer

Terms in this set (16)

What is horizontal gene transfer?
-gives genes to others
-donor cell contributes a part of the genome to recipient cell
What are the 3 types of horizontal gene transfer?
-transformation
-transduction
-bacterial conjugation
What is a competent cell?
-one that can take up DNA
What is transformation?
-one of conclusive pieces of proof that DNA is genetic material
-cells that can take up DNA are competent
-results from alterations in cell wall and cytoplasmic that allow DNA to enter or exit cell
What is an example of tranformation?
1. capsulated bacteria injected in mouse and mouse dies due to capsule causing immunity
2. non-capsulated bacteria injected in mouse and the mouse lives because phagocytes were able to kill the non-protected bacteria
3. capsulated bacteria is heated and then injected. Heated bacteria was killed so mouse was able to live
4. heat killed capsulated bacteria and live non-capsulated bacteria enter mouse. Gene transfer occurs so capsulated bacteria is alive again. mouse dies (recombination occurs)
What are the two types of transduction?
-generalized transduction
-specialized transduction
What is a phage?
-virus
What is generalized transduction?
-transducing phage carries random DNA segment from donor to recipient
What is specialized transduction?
-only certain donor DNA sequences are transcribed
What are the steps of transduction?
1. Bacteriophage injects its DNA into cell
2. Phage ezymes degrade host DNA
3. Cell synthesizes new phages that incorporate phage DNA and mistakenly host DNA
4. transducing phage (has host DNA) exits cell and binds to another cell
5. This time the host DNA doesn't degrade but gains more DNA through recombination because the phage had host DNA in it
What are plasmids?
-extra-chromosomal genetic material
-no part of genome
-in a separate place
-only helpful in certain situations
What can plasmids contain?
-resistance factors
-fertility genes (help bacteria to shape DNA)
-virulence genes (bacteria infection)
What is bacterial conjugation?
-how plasmids spread
-the sharing of DNA between bacteria of the same generation
What is the basic process of bacterial conjugation?
1. pillus/fimbriae attaches two cells together
2. hollow pillus allows transfer
3. in order for conjugation to occur, an F+ cell (sex pillus) needs to be there (fertile) to connect with a F- (non-fertile cell)
4. Process requires contact
5. makes F+ cells after conjugation
6. Plasmids get integrated into chromosome generating an hfr cell
7. Hfr conjugation transfers DNA but not fertility to an F- cell becuase it's too big
What is an Hfr cell?
-high frequency of recombination cell
A viable mixture of free DNA, competent F+ bacterial cells, and bacteriophage is treated with DNAse. Which horizontal gene transfer method might still be functional?
-transduction only because DNAse breaks free DNA and eliminates transformation
-no F+ takes out conjugation
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