Module 7 Molecular Genetics

Module 7—Genetics at the Molecular Level:DNA and RNA at Work

Read

Transgenic organisms other than bacteria and plants have also been created. A few examples of these transgenic organisms are listed below:

• goats that produce spider silk in milk for pharmaceutical products
• sheep milk that produces proteins to help treat cystic fibrosis
• cow’s milk that produces an iron transport protein that is added to infant formula
• chickens that can produce human proteins in the whites of their eggs
• mice used in biological experiments
• pigs whose organs can be donated to humans

Once a transgenic organism is produced, scientists will likely want to produce more of that organism. Creating a transgenic organism is a difficult, an expensive and a time-consuming task. In order for a herd of transgenic organisms to be created, scientists could wait many generations, or they can use cloning techniques to create “copies” of the transgenic organism. Cloning techniques allow for the ability to create hundreds of transgenic organisms in just one generation.

 

Cloning an organism uses specific somatic (body) cells from the genetic donor (animal you want to clone) and transplants the nuclei of these cells into the egg cells (with nuclei removed) of another organism. The resulting embryos are implanted into a surrogate mother. Read more about the cloning process on pages 655 and 656 in your textbook.

 

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Gene Replacement Therapy

Replacing defective genes in humans is a new way to prevent and/or treat genetic disorders. This new therapy is called gene replacement therapy. This type of therapy attacks the cause of the disorder instead of treating the symptoms. Most of the research trials have concentrated on treating somatic cells (somatic gene therapy). This type of treatment can only improve the health of the individual patient. A more controversial therapy, germ-line therapy modifies the genetic information in the egg and sperm cells and could eliminate the disorder in offspring. Currently germ-line therapy is banned in Canada. Read more about gene therapy, the use of DNA vectors to alter the genetic material in humans, and the controversy surrounding this new form of treatment on pages 660 and 661 of your textbook.

 

Discuss

As you do the following research, remember that technologies, their methods and use, the controversy, and the societal issues that can surround them are often part of the open response essay question on your Diploma exam.

 

A.  Read about “Ownership of Genetic Information” on page 653 and 654 of your textbook. Think about the following questions and create a discussion posting stating your opinions. Check out some of the other postings by your classmates and respond to at least two.

 

Who owns the genetic information of the transgenic organisms? Should companies have the right to sell DNA information to other companies without the permission of the people who provided the samples? Should companies that use DNA in medical research be required to share the results of their work with the individuals whose genetic information was used? What are the advantages and disadvantages of companies patenting genes like “Roundup-Ready”?

Lesson Summary

This lesson has discussed the processes and controversy involved in genetic engineering. You have learned about the steps needed to for recombinant DNA, including how DNA ligase is used to join the sticky ends created at the restriction site by restriction endonucleases. You have learned about different transgenic organisms and chimeras and discussed the advantages and disadvantages of these genetically altered organisms. You have learned about the mechanisms involved in cloning and gene therapy, and you have also discussed the controversy surrounding this science. Who owns DNA was one of the final topics of discussion in this unit. Many difficult social and ethical issues were raised in this lesson, and it will be very exciting and interesting to see what the future holds for genetic engineering. In the next lesson, you will see how the entire human DNA sequence was identified and how a knowledge of DNA sequences can help trace ancestral relationships.

 

Glossary

bioremediation: use of living cells to perform environmental clean-up tasks, such as using bacteria to degrade PCBs into harmless compounds

chimera: a genetically engineered organism that contains DNA from unrelated species

clones: genetically identical organisms

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

gene replacement therapy: the process of changing the function of genes to treat or prevent genetic disorders

genetic engineering: manipulation of genetic material to alter genes and blend plant, animal and bacterial DNA

germ-line therapy: gene therapy used to modify the genetic information carried in egg and sperm cells

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

recombinant DNA: a molecule of DNA that includes genetic material from different sources

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

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

somatic gene therapy: therapy that is aimed at correcting genetic disorders in somatic (body) cells

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

target sequence: in DNA replication, a short sequence of nucleotides within a strand of DNA recognized and cut by restriction endonucleases

transgenic organism: produced by incorporating the DNA form one organism into another to create a new genetic combination