15.1 What Is Biotechnology?. What Is Biotechnology?. Biotechnology can be defined as the use of technology to control biological processes as a means of meeting societal needs. 15.2 Transgenic Biotechnology. Transgenic Biotechnology.
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What Is Biotechnology? • Biotechnology can be defined as the use of technology to control biological processes as a means of meeting societal needs.
Transgenic Biotechnology • Human growth hormone is produced within a bacterium that has been made transgenic by means of incorporating a human gene.
Transgenic Biotechnology • A transgenic organism is an organism whose genome has stably incorporated one or more genes from another species. • Many biotechnology products are produced within transgenic organisms.
Restriction Enzymes • Restriction enzymes are proteins derived from bacteria that can cut DNA in specific places.
Restriction Enzymes 1. A portion of a DNA strand, highlighted here, has the recognition sequence GGATCC. 2. A restriction enzyme moves along the DNA strand until it reaches the recognition sequence and makes a cut between adjacent G nucleotides. “sticky ends” 3. A second restriction enzyme makes another cut in the strand at the same recognition sequence, resulting in a DNA fragment. DNA fragment Figure 15.3
Plasmids • Plasmids are small, extra-chromosomal rings of bacterial DNA that can exist outside of bacterial cells and that can move into these cells through the process of transformation.
Plasmids bacterium plasmid bacterial chromosome Figure 15.4
Getting Human Genes into Plasmids • Human DNA can be inserted into plasmid rings. • Scientists use the same restriction enzyme on both the human DNA of interest and the plasmids. • Complementary “sticky ends” of the fragmented human and plasmid DNA will bond together, splicing the human DNA into the plasmid. • This produces recombinant DNA.
Recombinant DNA • Recombinant DNA: two or more segments of DNA that have been combined by humans into a sequence that does not exist in nature.
Turning out Protein • Once plasmids have had human DNA spliced into them, the plasmids can then be taken up into bacterial cells through transformation.
Turning out Protein • As these cells replicate, producing many cells, the plasmid DNA inside them replicates as well.
Turning out Protein • These plasmids produce the protein coded for by the human DNA that has been spliced into them. • The result is a quantity of the human protein of interest.
human cell containing gene of interest bacterium plasmid bacterial chromosome DNA protein synthesis Use same restriction enzyme to snip plasmid. human protein of interest 1. Use restriction enzymes to snip gene of interest from the isolated human genome. recombinant DNA 2. Insert gene into plasmid (complementary sticky ends will fit together). transformation 3. Transfer the plasmid back into bacterial cell. replication 4. Let bacterial cells replicate. Harvest and purify the human protein produced by the plasmids inside the bacterial cells. bacterial clones Figure 15.5
Plasmids Are One Type of Cloning Vector • A cloning vector is a self-replicating agent that functions in the transfer of genetic material. • Viruses known as bacteriophages are another common cloning vector.
Real-World Transgenic Biology • A large number of medicines and vaccines are produced today through transgenic biotechnology.
Real-World Transgenic Biology • Transgenic organisms that are used for this purpose include not only bacteria but also yeast, hamster cells, and mammals such as goats.
Real-World Transgenic Biology • Transgenic food crops are planted in abundance today in the United States.
Real-World Transgenic Biology Figure 15.6
Reproductive Cloning • A clone is a genetically identical copy of a biological entity. • Genes can be cloned, as can cells and plants.
Reproductive Cloning • Reproductive cloning is the process of making adult clones of mammals of a defined genotype. • Dolly the sheep was a reproductive clone.
Reproductive Cloning • Today, reproductive cloning of mammals is carried out through variants of the process that was used with Dolly. • This process is called somatic cell nuclear transfer (SCNT).
Somatic Cell Nuclear Transfer (SCNT) • An egg cell has its nucleus removed and is fused with an adult cell containing a nucleus and, therefore, DNA. • The fused cell then starts to develop as an embryo and is implanted in a surrogate mother.
white sheep black-faced sheep 1. A cell was taken from the udder of a six-year-old white sheep and then allowed to divide many times in the laboratory. Meanwhile an egg was taken from a black-faced sheep. 2. One of the resulting udder cells was selected to be the “donor” cell for the cloning. Meanwhile, using a slender tube called a micropipette, researchers sucked the DNA out of the egg. egg cell (nucleus removed) udder cells 3. The donor cell and egg were put next to each other, and an electric current was applied to the egg cell. DNA 4. This caused the two cells to fuse and prompted an activation that reprogrammed the donor-cell DNA. This caused the fused cell to start developing as an embryo. embryo 5. After some incubation, the embryo was implanted in a third sheep, which served as the surrogate mother. Dolly surrogate mother 6. This mother gave birth to Dolly the sheep, which grew into an adult. Figure 15.8
Reproductive Cloning • Reproductive cloning can work in tandem with various recombinant DNA processes to produce adult mammals possessing special traits.
Reproductive Cloning • A cell can be made transgenic for such a trait and then used as the starting cell (the donor-DNA cell) in producing an adult mammal with the trait.
Human Cloning • A human clone would be a genetic replica of the person who provided the donor-DNA cell. • The donor and his or her clone would be genetically identical in the same way that identical twins are.
Cell Fates: Committed or Not? • Most cells in the adult human body have undergone commitment, a developmental process that results in cells whose roles are completely determined.
Cell Fates: Committed or Not? • Most muscle cells have undergone commitment, for example, and hence can be nothing but muscle cells and give rise to nothing but muscle cells.
Cell Reprogramming • Two promising methods exist for generating human cells that are needed to treat victims of accident or disease: • Production through embryonic stem cells • Production through induced pluripotent stem cells
Cell Reprogramming • Both methods use the reprogramming of cells to yield desired cell types.
Embryonic Stem Cells day 5 fertilization days 1–3 inner cell mass blastocyst Figure 15.9
Embryonic Stem Cells • Cells from the blastocyst’s inner cell mass, known as embryonic stem cells(ESCs), can give rise to all the different cell types in the adult human body.
Adult Stem Cells • ESCs stand in contrast to adult stem cells, which are found, in small numbers, in various types of tissues in the adult body.
Adult Stem Cells • These adult cells have demonstrated some ability to differentiate into various types of specialized cells and hence are the subject of continued research interest.
Adult Stem Cells • However, adult stem cells do not have the differentiation potential of ESCs, nor the ESC’s ability to continue to produce specialized cells generation after generation.
Induced Pluripotent Stem Cells • In 2007, two research teams developed a type of human stem cell not derived from an embryo: the induced pluripotent stem cell (iPS cell). • It was first produced by means of splicing four developmental genes into the genomes of ordinary adult skin cells.
Induced Pluripotent Stem Cells • iPS cells appear to have all the developmental power of ESC. • They hold promise of reducing problems of tissue rejection in medical transplantation procedures. • They are being widely used as a means of studying human disease.
Forensic Biotechnology • Identities of criminals, biological fathers, and disaster victims often are established today through the use of forensic DNA typing.
Forensic Biotechnology • Forensic DNA typing is the use of DNA to establish identities in connection with legal matters, such as crimes.
The Use of PCR • The polymerase chain reaction (PCR) is a technique for quickly producing many copies of a segment of DNA.
1. A researcher selects a DNA region of interest. double-stranded DNA 2. The DNA is heated, causing the two strands of the double helix to separate. single-stranded DNA 3. As the mixture cools, short DNA sequences called primers form base pairs with complementary DNA sequences on their respective strands. primers 4. DNA polymerase goes down the line, synthesizing complementary DNA strands. The end result is a doubling of the original DNA. double-stranded DNA 5. The process is repeated many times, doubling the amount of DNA each time. Figure 15.11
The Use of PCR • PCR is useful in situations, such as crime investigations, in which a large amount of DNA is needed for analysis, yet the starting quantity of DNA is small.
Finding Individual Patterns • Forensic DNA typing usually works through comparisons of short tandem repeat (STR) patterns that are found in all human genomes.
Finding Individual Patterns • Police will compare the STR pattern in a suspect’s DNA with the STR pattern in DNA that has been extracted from a crime scene.