Module 7 Molecular Genetics
Lesson 3.7.5
3.7.5 page 2
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genetic engineering: manipulation of genetic material to alter genes and blend plant, animal and bacterial DNA
recombinant DNA: a molecule of DNA that includes genetic material from different sources
Genetic engineering is used in the laboratory to manipulate genetic material. Genes from plants, animals, and bacteria can be inserted into a different organism’s genetic material. In the last lesson, an example of a goat producing silk in its milk was described. That is an example of genetic engineering. The gene for silk production from a spider was isolated and then inserted in the genetic material of the goat. This new combination of spider and goat DNA is called recombinant DNA.
restriction endonuclease: type of restriction enzyme that recognizes a specific, short sequence of nucleotides within, rather than at the ends of, a strand of DNA and cuts the strand at that particular point within the sequence
restriction enzyme: enzyme that cuts DNA at specific nucleotide sequences creating fragments
target sequence: in DNA replication, a short sequence of nucleotides within a strand of DNA recognized and cut by restriction endonucleases
restriction site: specific location within a short sequence of nucleotides in a strand of DNA at which restriction endonucleases will cut
restriction fragment: small segments of DNA cut from a DNA molecule by a restriction endonucleases
sticky end: short sequence of unpaired nucleotides remaining at each end of a restriction fragment on a single strand of DNA after an endonuclease makes a staggered cut at the restriction site
DNA ligase: enzyme that splices together Okazaki fragments on the lagging strand or sticky ends that have been cut by a restriction endonuclease during DNA replication
Researchers will use restriction endonucleases, a specific group of restriction enzymes that are able to “cut” the interior of DNA molecules within specific short sequences of nucleotides called target sequences. The actual site where the DNA is cut is called the restriction site. The target sequences and restriction sites are specific for different endonucleases. Figure 18.18 on page 648 shows the target sequence of GAATTC for a restriction endonuclease. Notice the restriction site within the target sequence. The small fragments of DNA created from this cleavage are called restriction fragments. If the same endonucleases are used to cut DNA from another organism, the restriction fragment’s sticky ends can base-pair with other organisms’ restriction fragments. DNA ligase can be used to splice these fragments together. Review the processes involved in genetic engineering by reading pages 647 to 648 in your textbook.
Watch and Listen
This video titled Genetic Engineering: The Science of Manipulating DNA goes through genetic engineering in more detail.
As you watch the video, pay particular attention to how the students model the restriction endonuclease’s action using paper. Stop viewing when you reach the section about “gel electrophoresis.”
Module 7: Lesson 5 Assignment—Part 1
Recreating the First Chimera
Read "Thought Lab 18.4: Recreating the First Chimera”.
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In the above “Recreating the First Chimera” assignment, you saw how scientists added foreign DNA (an amphibian gene) into the circular plasmid DNA of bacteria. Bacteria have been used in this way since 1982 to synthesize human insulin to treat diabetes. Genetically engineered bacteria have also been used to produce other medicines such as Human Growth Hormone to treat dwarfism, and clotting factors to treat hemophilia. Bioremediation is another of use of genetically altered bacteria. Bacteria’s metabolic functions can be enhanced through genetic engineering to allow them to clean up soils polluted with PCBs, clean up oil spills, filter air from factory smoke stacks and remove heavy metals from water.
plasmid: small self-duplication loop of DNA in a prokaryotic cell that is separate from the main chromosome and contains from one to a few genes
bioremediation: use of living cells to perform environmental clean-up tasks, such as using bacteria to degrade PCBs into harmless compounds
transgenic organism: produced by incorporating the DNA form one organism into another to create a new genetic combination
Genetic engineers have also been able to insert foreign DNA into plants and animals. Transgenic organisms are the result of these procedures. One example of a transgenic plant is golden rice, described in figure 18.22 on page 655 of your textbook. This figure shows the 4 different plant and fungus genes that have been added to this rice in order to increase its iron and vitamin A content. Read more about transgenic plants on page 655 and answer the following question to check your understanding.
Self-Check
Complete this Self-Check activity.
Discuss
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Some genetically modified plants have much controversy surrounding them. Bt corn is a genetically modified organism (GMO) that makes up about 50% of the corn crops grown in Canada. Bt is a naturally occurring soil bacterium called bacillus thuringiensis that produces a protein that acts as an insecticide. Scientists isolated this protein from Bt and inserted it into the corn DNA. The resulting transgenic Bt corn produces the Bt protein insecticide, therefore killing pests feeding on the plant. In 1999, a study from Cornell University showed that monarch caterpillars who fed on milkweed covered in Bt corn pollen grew more slowly and had higher mortality rates. News agencies picked up this story quickly, and many articles and reports resulted. Search the internet for a report. about this study. There was much controversy surrounding the results of this study.