Chapter 13: Genetic Engineering

Selective Breeding

   Has been occurring for thousands of years Ex: (dog breeds, agriculture) Takes advantage of naturally occurring traits in a population Two types

Selective Breeding

   Hybridization: crossing two dissimilar organisms to get the best traits of both organisms hybrids are often hardier/stronger than either parent ex: mules (cross between horse and donkey), ligers (lion/tiger)

Selective Breeding

   Inbreeding: crossing two organisms that are very similar to retain desirable characteristics. Can lead to recessive genetic disorders appearing frequently because the organisms are so similar genetically. Ex. Maintaining “purebred” dog breeds

Increasing Variation

    If the desired characteristic is it causing the right effect not present, scientists have induced mutations in hope of Success stories:  Oil-eating bacteria- used to clean up oil spills Creating polyploidy (3+ sets of chromosomes) plants- usually larger and stronger Examples: bananas, citrus

Genetic Engineering

 That was the “old” way of manipulating inheritance. Now, we can isolate specific DNA sequences and modify the code in what is called genetic engineering.

How do they get it out of the cells?

o DNA extraction- lysing the cells and separating the excess cell parts from the DNA by using a centrifuge Dissolved DNA cell junk

How do they cut the pieces they want?

 Restriction enzymes- they cut DNA at a specific site (100s of them that identify different sequences of base pairs know as recognition sequences- they are a palindrome- read the same 5’-3’ in each direction)  CTTAAG is cut GAATTC CTTAAG GAATTC

 The two ends are known as “Sticky” because they reattach to a complementary end very easily because if chemical attractions

How are the pieces identified?

    Using gel electrophoresis Different fragments end up being different lengths They are run through gel electrophoresis where electrical current pull DNA fragments through an agarose gel. DNA mixtures are placed in a well in agarose and electrical current is switched on.

The small fragments travel faster, and the larger fragments cannot travel as far.

DNA fingerprint produced by gel electrophoresis

So what does that tell us?

   relatedness of individuals (paternity tests), relatedness of groups of organisms (closest related species), or relatedness of DNA to suspects and evidence in a crime scene.

Genetic Engineering

 Gene sequencing: using a gel electrophoresis method ( organisms)  ) or using a machine (below), scientists can figure out genes and entire genomes (all the genes in an

How can we sequence DNA?

   Mix unknown DNA fragment with DNA polymerase and nucleotides to copy the DNA.

The nucleotides added will also have special dideoxynucleotides (didNTP) with attached dyes.

Newly synthesized DNA will be made but will stop each time a didNTP nucleotide is added.

How can we sequence DNA?

 The DNA is run on a gel and the fragments will make a colored banding pattern in the order of bases (A, T, G, or C)

Genetic Engineering

   We can now find and isolate certain genes.

you can test for certain genetic disorders, and predict chances of inheritance   scientists can study the gene’s function and how to treat people with the genetic disorder Ex: what gene causes diabetes? Breast cancer?

We have completed the Human Genome Project mapping all human genes

Gene Therapy

 Gene Therapy: a faulty gene is replaced with a normal working gene

How do we get a lot of copies of a specific DNA sequence we want?

 PCR- Polymerase Chain Reaction   a primer is added to the beginning of the isolated desired gene DNA is heated to break the hydrogen bonds between the nitrogenous bases   DNA polymerase attaches and replicates sides, using both as templates Copies are made at an exponential rate of only the desired gene

Recombinant DNA

  Manipulating the presence or absence of genes by adding or cutting out gene sequences Combining DNA from two different sources by cutting with the same restriction enzymes creates DNA that has been modified

 Transformation- a cell takes in DNA from outside the cell and incorporates it into its own DNA (bacterial plasmids, chromosomes in plants and animals)

Applications of Genetic Engineering

  Transgenic Organisms: organisms that contain DNA from other species   Transgenic bacteria: can produce human insulin (for diabetes) human growth hormone  blood clotting factor (for hemophilia)

Transgenic Organisms

    Transgenic animals: study human genes in animals produce organisms that can make human proteins cows that can grow faster with multiple copies of growth hormone A natural protein produced in the milk of GEM and other transgenic cows kills the bacteria that cause mastitis.

Transgenic Organisms

    Transgenic plants: genetically modified foods seedless grapes and watermelons rice with vitamin enhancement pest-resistant crops (so chemical pesticides do not need to be used)

Cloning

   Cloning: creating an organism whose genes are exactly the same single parent as a All bacteria and organisms that reproduce asexually are technically clones Multicellular organisms are not as easy to clone- a mammal was cloned officially in 1997—Dolly

Cloning

    The nucleus of an adult, donor egg is removed This empty egg is fused with another adult somatic cell’s NUCLEUS (diploid, 2N) The cell is stimulated with electric shock to divide normally by mitosis and the zygote is implanted into a surrogate mother The baby is born of the surrogate and has the EXACT same genes as the organism who donated the 2N nucleus.

The difference between regular reproduction and cloning  (click)

Cloning videos

  Scientists removing the Egg nucleus: http://learn.genetics.utah.edu/content/tec h/cloning/whatiscloning/images/enucleatio n.mpg

Scientists inserting the donor somatic cell nucleus into the empty egg: http://learn.genetics.utah.edu/content/tec h/cloning/whatiscloning/images/transfer.m

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Stem Cells

   Every cell in your body originated from single cell (zygote) that was the fusion of egg and sperm. It divides into a mass of cells that do not yet have a defined function- these cells are said to be undifferentiated. Cells that are undifferentiated can give rise to many types of cells: blood cells, skin cells, nerve cells, etc.

What is a stem cell? (click) 

Stem Cells- What is the difference?

 Let’s watch the stem cell animations.

Stem Cells

 Embryonic stem cells- cells from very early stages of development that can become ANY kind of cell, but they are harder to manipulate and have the risk of rejection by the recipient, ethical objections because the embryo is destroyed during the process of harvesting the cells

Stem Cells

 Adult stem cells- cells from certain region in our bodies that are only partially differentiated and can be manipulated into becoming a limited kind of cell, less chance of being rejected, fewer ethical objections

Stem Cells

 All stem cells—regardless of their source— have three general properties: they are capable of dividing and renewing themselves for long periods; they are unspecialized; and they can give rise to specialized cell types.

  What is the purpose of stem cell therapy? To restore tissues that have been damaged by injury or disease that cannot repair themselves

What are some concerns with this new Biotechnology?

 Ethics: moral principles and values that a society should adhere to in determining the use of scientific discoveries

What are some concerns with this new Biotechnology?

   What is ethically acceptable to use while testing on animals?

What could genetically modified crops do to the environment?

What does consuming genetically modified food do to us long term?

What are some concerns with this new Biotechnology?

   Once able to find and fix faulty genes with gene therapy, what is the line we draw on fixing genes? Could we fix not only faulty genes, but undesirable ones? Could we choose our children’s eye color?

If we can test for genetic disorders at birth, who can access this information? Could discrimination occur based on your genes?