Ch. 9: Frontiers of Biotechnology

• Humans have been influencing the genetics of organisms since the beginning of agriculture approximately 12,000 years ago.– Selective breeding: Choosing organisms with the

best traits to produce the next generation.

Inbreeding: type of selective breeding in which organisms that are closely related are mated, in order to maintain desired traits.

Hybridization: type of selective breeding that mates closely related subspecies to blend desired traits, offspring are often infertile.

• In the last century, humans developed a process called genetic engineering.– Genetic engineering changes an organism’s DNA

to give the organism new traits.

Restriction enzymes cut DNA.

• Restriction enzymes act as “molecular scissors.” – come from various types of bacteria– allow scientists to more easily study and manipulate

genes– cut DNA at a specific nucleotide sequence called a

restriction site

• Different restriction enzymes cut DNA in different ways.

– each enzyme has a different restriction site

Recombinant DNA Technology

• Recombinant DNA involves inserting the genes of one organism into the into the DNA of another organism.– Bacteria are most commonly used for this type of

technology because they are cheap and plentiful to grow.

How to Make Recombinant DNA:

1. Restriction enzymes are used to find and cut out specific sequences of DNA in both the “new” DNA and the “old” DNA. DNA in bacteria is typically found in a simple ring called a plasmid.

2. Enzymes help bind the donor DNA into the plasmid (each was left with a “sticky end” that bonds to each other.

3. The plasmid is introduced into the bacterial cells, and the bacteria unknowingly replicates the new DNA during reproduction.

Transgenic Organisms

• A transgenic organism has one or more genes from another organism inserted into its genome.

Transgenic Organisms

• Transgenic bacteria can be used to produce human proteins.– Example: Insulin

Transgenic Organisms

• Transgenic plants are engineered to be superior to their “normal” relatives. They are called GM (genetically modified).– drought resistant– pest resistant– modified to make medicines

Transgenic Organisms

• Transgenic animals are engineered for a number of reasons:– larger and healthier– models for human– treatment for humans

• Scientists have concerns about some uses of genetic engineering.– possible long-term health effects of eating GM foods– possible effects of GM plants on ecosystems and

biodiversity

PCR uses polymerases to copy DNA segments.

• PCR makes many copies of a specific DNA sequence in a few hours.

target sequence of DNA

• PCR amplifies DNA samples.• PCR is similar to DNA replication.

PCR is a three-step process.

• PCR uses four materials.– DNA to be copied– DNA polymerase– A, T, C, and G nucleotides– two primers

DNA strands

polymerase

nucleotides

primer 1

primer 2

DNA strands

polymerase

nucleotides

primer 1

primer 2

• The three steps of PCR occur in a cycle.

– heat is used to separate double-stranded DNA molecules

– primers bind to each DNA strand on opposite ends of the segment to be copied

– DNA polymerase binds nucleotides together to form new strands of DNA

• Each PCR cycle doubles the number of DNA molecules.

Cloning

• A clone is a genetically identical copy of a gene or of an organism.

• Cloning occurs in nature.

– bacteria (binary fission)– some plants (from roots)– some simple animals (budding, regeneration)

How to Clone Using Nuclear Transfer:

1. The nucleus is removed from a donor egg cell.

2. Nucleus of a cell (can be any body cell) from the animal to be cloned is implanted in the egg and stimulated with electricity.

3. In mammals, if fusion occurs and an embryo forms, the embryo is placed in the womb of a female and if implanted, the embryo will form like a normal baby.

How to Clone:

• Cloning has potential benefits.

– organs for transplant into humans– save endangered species

• Cloning raises concerns.– low success rate– clones “imperfect” and less healthy than original animal– decreased biodiversity

Other Uses of Biotechnology

• Biotechnology is the use and application of living things and biological processes.– DNA fingerprints are a

common use of biotechnology.

Restriction maps show the lengths of DNA fragments.

• Gel electrophoresis is used to separate DNA fragments by size.– A DNA sample is cut with restriction enzymes.– Electrical current pulls DNA fragments through a gel.– Smaller fragments move faster and travel farther

than larger fragments.– Fragments of different sizes appear as bands on the

gel.

A DNA fingerprint is a type of restriction map.

• DNA fingerprints are based on parts of an individual’s DNA that can by used for identification.– based on noncoding regions of DNA– noncoding regions have repeating DNA sequences– number of repeats differs between people– banding pattern on a gel is a DNA fingerprint

DNA fingerprinting is used for identification.

• DNA fingerprinting depends on the probability of a match.– Many people have the

same number ofrepeats in a certainregion of DNA.

– The probability that two people share identicalnumbers of repeats inseveral locations isvery small.

(mother) (child 1) (child 2) (father)

– Individual probabilities are multiplied to find the overall probability of two DNA fingerprints randomly matching.

– Several regions of DNA are used to make DNA fingerprints.

1 1 1 1500 90 120 5,400,000 1 chance in 5.4 million peoplex x = =

• DNA fingerprinting is used in several ways.

– evidence in criminal cases

– paternity tests– immigration requests– studying biodiversity

– tracking genetically modified crops

Biotechnology in Genomics

• Genomics is the study of genomes.– can include the sequencing

of the genome– comparisons of genomes

within and across speciesthe amount of DNA in an organism is NOT equivalent to how advanced they are!

• The Human Genome Project has sequenced all of the DNA base pairs of human chromosomes.

– analyzed DNA from a few people

– still working to identify and map human genes

Genetic screening can detect genetic disorders.

• Genetic screening involves the testing of DNA.– determines risk of having

or passing on a geneticdisorder

– used to detect specificgenes or proteins

– can detect some genesrelated to an increasedrisk of cancer

– can detect some genesknown to cause geneticdisorders

DMD N

• A karyotype is a picture of all chromosomes in a cell.

X Y

• Karyotypes can show changes in chromosomes.

– Nondisjunction: an error in meiosis that results in an extra or a loss of a chromosome

– deletion of part of a chromosome or duplication of part of a chromosome

Gene Therapy

• Gene therapy replaces defective or missing genes, or adds new genes, to treat a disease.

• Several experimental techniques are used for gene therapy.

– Viruses-genetically engineered viruses used to “infect” a patient’s cells, by inserting genes into viruses that are used to infect a person’s cells.

– Immune system-insert gene to stimulate immune system to recognize and attack cancer cells

– Suicide genes- insert “suicide” genes into cancer cells that activate a drug to kill the cells; normal cells without the gene are not affected.

• Gene therapy has many technical challenges.

– inserting gene into correct cells– controlling gene expression– determining effect on other genes