Download Chapter 13: Genetic Engineering

Chapter 13: Genetic Engineering and Biotechnology
I. Selective Breeding
a. Has been occurring for thousands of years Ex: (dog breeds, agriculture)
b. Takes advantage of naturally occurring traits in a population
c. Hybridization: crossing two dissimilar organisms to get the best traits of
both organisms
i. hybrids are often hardier/stronger than either parent
ii. ex: mules (cross between horse and donkey), ligers (lion/tiger)
d. Inbreeding: crossing two organisms that are very similar to retain desirable
characteristics.
i. Can lead to recessive genetic disorders appearing frequently
because the organisms are so similar genetically.
ii. Ex. Maintaining “purebred” dog breeds
II. Increasing Variation
a. If the desired characteristic is not present, scientists have induced
mutations in hope of it causing the right effect
b. Success stories:
i. Oil-eating bacteria- used to clean up oil spills
ii. Creating polyploidy (3+ sets of chromosomes) plants- usually
larger and stronger
1. Examples: bananas, citrus
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.
III. How do they get it out of the cells?
a. DNA extraction- lysing the cells and separating the excess cell parts from
the DNA (using a centrifuge)
IV. How do they cut the pieces they want?
a. Restriction enzymes- they cut DNA at a specific site (100s of them that
identify different sequences of base pairs know as recognition sequencesthey are a palindrome- read the same 5’-3’ in each direction)
b. CTTAAG is cut
CTTAAG
GAATTC
GAATTC
o The two ends are known as “Sticky” because they reattach to a
complementary end very easily (because of chemical attractions)
V. How are the pieces identified? Gel electrophoresis
a. Different fragments end up being different lengths
b. 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.
c. The small fragments travel faster, and the larger fragments cannot travel as
far.
VI. So what does that tell us?
a. banding patterns are unique to an individual
b. DNA fingerprints can be used to compare 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.
VII. How can we sequence DNA?
a. using a gel electrophoresis method or using a machine, scientists
can figure out genes and entire genomes (all the genes in an
organisms)
b. Mix unknown DNA fragment with DNA polymerase and
nucleotides to copy the DNA.
c. The nucleotides added will also have special dideoxynucleotides (didNTP)
with attached dyes.
d. Newly synthesized DNA will be made but will stop each time a
DNA fingerprint
didNTP nucleotide is added.
produced by gel
e. The DNA is run on a gel and the fragments will make a colored
electrophoresis
banding pattern in the order of bases (A, T, G, or C)
f. Watch the animation on the website highlighted in the resources
page of my website.
g. Sequencing them allows us to find and isolate certain genes.
i. you can test for certain genetic disorders, and predict chances of
inheritance
ii. scientists can study the gene’s function and how to treat people
with the genetic disorder
h. We have completed the Human Genome Project mapping all human genes
i. Gene Therapy: a faulty gene is replaced with a normal working gene
VIII. How do we get a lot of copies of a specific DNA sequence we want?
a. PCR- Polymerase Chain Reaction
i. a primer is added to the beginning of the isolated desired gene
ii. DNA is heated to break the hydrogen bonds between the
nitrogenous bases
iii. DNA polymerase attaches and replicated sides, using both as
templates
iv. Copies are made at an exponential rate of only the desired gene
IX. Recombinant DNA- manipulating the presence or absence of a gene by adding or
cutting out gene sequences
a. Combining DNA from two different sources by cutting with the same
restriction enzymes creates DNA that has been modified ( DNA from two
different sources)
b. Transformation- a cell takes in DNA from outside the cell and
incorporates it into its own DNA (bacterial plasmids, chromosomes in
plants and animals)
X. Applications of Genetic Engineering
a. Transgenic Organisms: organisms that contain DNA from other species
i. Transgenic bacteria:
1. can produce human insulin (for diabetes)
2. human growth hormone
3. blood clotting factor (for hemophilia)
ii. Transgenic animals:
1. study human genes in animals
2. produce organisms that can make human proteins
3. cows that can grow faster with multiple copies of growth
hormone
iii. Transgenic plants: genetically modified foods
1. seedless grapes and watermelons
2. rice with vitamin enhancement
3. pest-resistant crops (so chemical pesticides do not need to
be used)
XI. Cloning: creating an organism whose genes are exactly the same as a single parent
a. All bacteria and organisms that reproduce asexually are technically clones
b. Multicellular organisms are not as easy to clone- a mammal was cloned
officially in 1997—Dolly
1. The nucleus of an adult, donor egg is removed
2. This empty egg is fused with another adult somatic cell’s
NUCLEUS (diploid, 2N)
3. The cell is stimulated with electric shock to divide
normally by mitosis and the zygote is implanted into a
surrogate mother
4. The baby is born of the surrogate and has the EXACT same
genes as the organism who donated the 2N nucleus.
ii. Why would we clone? To clone genetically engineered animals for
research, revive endangered or extinct species, clone a deceased
pet