Bubble boy (SCID) popularized in the 1970s of a young boy in Texas who survived to the age of 12 in a sealed environment. ADA defect: deoxyadenosine produced in response to DNA degradation. Is converted to deoxynucleotides, which inhibit white blood cell proliferation. ADA converts deoxyadenosine to deoxyinosine. Gamma chain is linked to IL-2 receptor, required for T-cell maturation from bone stem cells.
Humans have improved on nature’s support of plant and animal growth since they discovered that the loosening of soil and planting of seeds could result in new plants. Even prior to that discovery, they probably aided plant growth by keeping animals away from plans until they yielded fruit or other plant parts which were edible by humans.
History documents the domestication of the dog, horse, sheep, goats, ox, and other animals thousands of years ago. Improvement by selection soon followed. Improvement by selection means picking the best plants and animals for producing the next generation. As people bought, sold, bartered, and traded, they were able to get animals which had desirable characteristics, such as speed, gentleness, strength, color, size, milk production, and the like. By mating animals with characteristics that humans preferred, the offspring of those animals would tend to imitate the characteristics of the parents and further intensify the desired characteristics. By accident, the owner was practicing selective breeding or the selection of parents to get desirable characteristics in the offspring. The chariot armies of the Egyptians and Romans; the might of the Chinese emperors; the speed of the invading barbarians into northern Europe; the strength of mounts carrying armored knights into battle; and the evasive Arabians of the desert’ all provide convincing testimony to early successes at breeding horses for specific purposes.
This slide shows the basic steps of plant tissue culture. Some plant part is placed is on a defined culture media. That media induces the the tissue to develop callus. Callus is an undifferentiated mass of cells. These cells then grow into plant shoots, which are later rooted. The small seedling will then grown into a mature, seed-producing plant. When developing transgenic plants, the transformation cassette is introduced into that plant part that can be induced to grow new plants.
In 1988, California scientists made the first outdoor tests of ice-minus. Ice-minus is bacteria that was genetically altered to retard frost formation on plant leaves. Synthetic chemicals are now available to protect fruit crops when temperatures fall 4 to 6 degrees below what would normally damage the fruiting process. Similarly in 1988, genetically altered bacteria was injected into elm tress in an effort to control the deadly Dutch Elm disease. Further, bacteria was genetically engineered so they turn a brilliant shade of blue in the presence of a compound called X-Gal. Such bacteria can be easily detected and traced in experimental or real-life situations. The ability to so mark organisms has made biotechnology a safer and more manageable enterprise. In animal science, the hormone bovine somatotropin has long been know for its stimulation of increased milk production in cows. However, it was not available for commercial use until bacteria was altered to produce the hormone. Another example of hormone production by genetically altered bacteria is an animal hormone called porcine somatotropin, which increases meat production in swine. In plant science, Roundup and Liberty Ready Corn and Soybeans and BT Corn are examples of where genes have been altered enabling herbicide resistance and insect control through biotechnology.
What is biotechnology ？ United Nations Convention on Biological Diversity ： "Any technological application that uses biological systems, living organisms, or derivatives thereof, to make or modify products or processes for specific use."
Who ？ Prof. Tsui Lap Chee ？ Profession ？ Vice-Chancellor of HKU Academic contributions? identified the defective gene, namely Cystic fibrosis transmembrane conductance regulator (CFTR), that causes cystic fibrosis
Transfer of this material into target cells (gene delivery)
Integration of DNA into target cell genome
Correction of defect
Contributions of gene therapy: Good news : Promising advances during the last two decades in recombinant DNA technology . Bad news : Efficacy in any gene therapy protocol not definitive. 1. Shortcomings in all current gene transfer vectors. 2. Inadequate understanding of biological interactions of vector and host.
Treatment of S evere C ombined I mmuno D eficiency (SCID)
Genetic defects cause decreased T and B cells.
Affects 1-75,000 births.
Mostly males (most common form is X-linked)
Cause: ADA (adenine deaminase) deficiency
Bone marrow transplant
10-3-02 : France and US (FDA) halted SCID gene therapy due to leukemia-like side effects in one child. Not clear whether this is related to the gene therapy itself. 1/14/03: FDA suspended 30 gene therapy trials using retrovirus vectors due to another case of leukemia. clinical trials results : Detectable levels of T cells containing the introduced gene were found in the blood within 30 and 60 days, respectively, and their numbers increased progressively until normal levels were reached. After 3 months, the patients were also able to make antibodies in response to vaccination against diphtheria, tetanus, and pertussis.
June 2000 completion of a working draft of the entire human genome
February 2001 analyses of the working draft are published in Nature
Some results Take a look at human chromosome: http://www.ensembl.org/Homo_sapiens/ Home page of the human genome project http://www.ornl.gov/sci/techresources/Human_Genome/home.shtml
Characteristics / number of genes • The total number of genes is estimated at 30,000 to 35,000 much lower than previous estimates. • Almost all (99.9%) nucleotide bases are exactly the same in all people. (Side track questions: any 2 chimpanzees are more dislike than any 2 human, why?) • The functions are unknown for over 50% of discovered genes.
• Over 30 genes have been pinpointed and associated with some diseases (e.g. breast cancer, muscle disease, deafness, and blindness).
Additionally, finding the DNA sequences underlying such common diseases provide focused targets for the development of effective new therapies.
In the past, researchers studied one or a few genes at a time. With whole-genome sequences known, they can approach questions systematically and on a grand scale.
Discussion Questions 1. If the genome study obtain a franchise,how can we protect the right of the poor? 2. Now, the main area of application of the genome study is for medical purpose. However, with the same technique, it is also possible to manipulate genes for other purposes, such as increasing the longevity of life and I.Q. If then, is it ethical to create such "perfect" human beings? 3. Is it ethical to change the genes of other plants and animals? What are the risks behind? 4. It may be possible to prepare a tailor-made health-care program for each individual according his or her genes. Will the privacy of individuals be respected?
technology involved in removing, modifying, or adding genes to a DNA molecule
Cloning DNA into a Plasmid Both plasmid and foreign DNA have sticky Eco R I ends Insertion into E. coli (transformation) Agar plates contain antibiotic. Grow at 37 °C Place 1 colony in liquid media + antibiotic. Grow at 37 °C Purify Plasmid DNA (Billions of copies)
Add vast excess of the primers and heat mixture to 75 o C
This causes DNA strands to separate by breaking hydrogen bonds between bases
4. Cool to 15 o C. Primers hydrogen bond ( anneal ) to complementary strands 5. Add DNA polymerase and all four types of nucleotides. The polymerase (enzyme used in DNA replication) will fill in the rest of the two strands.
You now have two identical copies of the DNA you started with. 6. Repeat steps. Heat to break hydrogen bonds. Cool to anneal more primers (still there in vast excess). Allow DNA polymerase to fill in the remaining strands. Two strands of DNA become four. Etc…Etc…Etc…..
Minisatellites (VNTRs = variable number tandem repeats)
Repeated units of 5 to several 10 bp
Microsatellites (STRs = short tandem repeats)
Repeated units of 2-6 bp
How to make Antisense RNA mRNA and asRNA can form RNA/RNA duplex, which actually results in formation of 20-22 nts small RNA that trigger the degradation of mRNA transcribed region 5’ control region 3’ control region mRNA transcribed region 5’ control region 3’ control region Antisense mRNA (asRNA)
Baby and mother are expected to share on allele, and the baby and father the other allele.
If baby and father do not share a common allele, the “father” is not the father.
If the baby and father do share a common allele, paternity is possible, but not proven, because other men in the population also carry the allele at some frequency.
Forensics • identify potential suspects whose DNA may match evidence left at crime scenes • exonerate persons wrongly accused of crimes • identify crime and catastrophe victims
Clearly, suspect one is the match….. If all RFLP and STR regions are considered, there is a one in 3.4 billion chance of error. This means there may be one other person on the planet that would be too similar to tell the difference. If other VNTR regions are also considered, the chances of error go way, way down