1. CHAPTER 12 DNA Technology and the Human Genome
Modules 12.1 – 12.6

2. From E.Coli to a Map of Our Genes
Research on E. coli revealed that these bacteria have a sexual mechanism that can bring about the combining of genes from two different cells
This discovery led to the development of recombinant DNA technology
a set of techniques for combining genes from different sources

3. DNA technology has many useful applications
The Human Genome Project
The production of vaccines, cancer drugs, and pesticides
Engineered bacteria that can clean up toxic wastes

4. 12.1 In nature, bacteria can transfer DNA in three ways
BACTERIA AS TOOLS FOR MANIPULATING DNA
12.1 In nature, bacteria can transfer DNA in three ways
Transformation, the taking up of DNA from the fluid surrounding the cell
DNA enters cell
Fragment of DNA from another bacterial cell
Bacterial chromosome (DNA)
Figure 12.1A

5. Recipient cell (“female”)
Transduction, the transfer of bacterial genes by a phage
Conjugation, the union of cells and the DNA transfer between them
Mating bridge
Phage
Fragment of DNA from another bacterial cell (former phage host)
Sex pili
Donor cell (“male”)
Recipient cell (“female”)
Figure 12.1B
Figure 12.1C

6. The transferred DNA is then integrated into the recipient cell’s chromosome
Donated DNA
Degraded DNA
Crossovers
Recipient cell’s chromosome
Recombinant chromosome
Figure 12.1D

7. 12.2 Bacterial plasmids can serve as carriers for gene transfer
F factor (integrated)
An F factor is a DNA segment in bacteria that enables conjugation and contains an origin of replication
Male (donor) cell
Origin of F replication
Bacterial chromosome
F factor starts replication and transfer of chromosome
Recipient cell
Only part of the chromosome transfers
Figure 12.2A
Recombination can occur

8. F factor (plasmid)
An F factor can exist as a plasmid, a small circular DNA molecule separate from the bacterial chromosome
Male (donor) cell
Bacterial chromosome
F factor starts replication and transfer
Plasmids
Plasmid completes transfer and circularizes
Cell now male
Figure 12.2B, C

9. 12.3 Plasmids are used to customize bacteria: An overview
Plasmids are key tools for DNA technology
Researchers use plasmids to insert genes into bacteria

10. 1 2 3 4 5 Cell containing gene of interest Bacterium Plasmid isolated
DNA
isolated 3
Gene inserted into plasmid
Bacterial chromosome
Plasmid
Gene of interest
Recombinant DNA (plasmid)
DNA 4
Plasmid put into bacterial cell
Recombinant bacterium 5
Cell multiplies with gene of interest
Copies of gene
Copies of protein
Gene for pest resistance inserted into plants
Clones of cell
Protein used to make snow form at higher temperature
Gene used to alter bacteria for cleaning up toxic waste
Protein used to dissolve blood clots in heart attack therapy
Figure 12.3

11. 12.4 Enzymes are used to “cut and paste” DNA
Restriction enzyme recognition sequence
Restriction enzymes cut DNA at specific points
DNA ligase “pastes” the DNA fragments together
The result is recombinant DNA 1
DNA
Restriction enzyme cuts the DNA into fragments
Restriction enzyme cuts the DNA into fragments 2
Sticky end
Addition of a DNA fragment from another source 3
Two (or more) fragments stick together by base-pairing 4
DNA ligase pastes the strand 5
Figure 12.4
Recombinant DNA molecule

12. 12.5 Genes can be cloned in recombinant plasmids: A closer look
Bacteria take the recombinant plasmids and reproduce
This clones the plasmids and the genes they carry
Products of the gene can then be harvested

13. Bacterial clone carrying many copies of the human gene1
Isolate DNA from two sources
Human cell
E. coli 2
Cut both DNAs with the same restriction
enzyme
Plasmid
DNA
Gene V
Sticky ends 3
Mix the DNAs; they join by base-pairing 4
Add DNA ligase to bond the DNA covalently
Recombinant DNA plasmid
Gene V 5
Put plasmid into bacterium by transformation 6
Clone the bacterium
Bacterial clone carrying many copies of the human gene
Figure 12.5

14. 12.6 Cloned genes can be stored in genomic libraries
Recombinant DNA technology allows the construction of genomic libraries
Genomic libraries are sets of DNA fragments containing all of an organism’s genes
Copies of DNA fragments can be stored in a cloned bacterial plasmid or phage
Genome cut up with restriction enzyme
Recombinant plasmid
Recombinant phage DNA OR
Phage
clone
Bacterial clone
Plasmid
library
Phage
library
Figure 12.6