Download DNA Technology Notes

DNA Technology Notes
Restriction Enzymes
Scientists use several techniques to manipulate DNA (cloning = copying genes, transferring
genes between organisms, etc.)
DNA must first be extracted and precisely cut so that it can be studied.
Restriction enzymes (or molecular scissors) cut DNA at a certain nucleotide sequence called a
restriction site (4-6 base pairs long). REs come from bacteria that use them as a protection
against invaders (ex. Cut up the DNA of the viruses). REs restrict (or decrease) the effect of a
virus on the bacterial cell.
Some REs cut straight across
Some REs make staggered
a DNA —> “Blunt ends”
cuts —> “Sticky ends” (Velcro)
Palindromic Sequence - Reflects the same
Sequence on both sides
Result - DNA fragments with different lengths. The next step in the research is often the
separation of the DNA fragments by Gel Electrophoresis.
Gel Electrophoresis
An electrical current separates DNA fragments by size (cut by restriction
enzymes).
Electricity moves DNA because DNA is negatively (-) charged and likes to go to
positive (+) end.
* Bigger fragments move slower
* Smaller fragments are faster and are closer to positive (+) end
* Gel matrix with pores — large fragments slow down.
* Restriction map —the pattern of DNA fragments (bands) that shows up on the
gel, which shows the sizes of DNA fragments.
Learning Check
1. If the DNA molecule in your booklet was cut at the
following places, which piece would be closest to the
wells (where DNA was placed into gels) and which
would be the closest to the + end?
B closest to the wells/A farthest and closest to +
end
2. DNA electrophoresis is used to study evolutionary
relationships of species. According to the diagram of
species A, X, Y and Z, which species has the most DNA in
common with species A?
Species Z—the fewer differences in DNA the more
closely related
DNA Fingerprinting
Used in a person’s identification, criminal and parental identification at the
molecular level. It can show relationships among family members.
In parentage– tests can not absolutely PROVE parentage but can absolutely
disprove.
A DNA fingerprint is a type of restriction map.
99.9% of human DNA is the same in EVERY person except monozygotic
(identical twins)
The greatest differences in the DNA among people are found in regions of
the genome that are NOT parts of genes (Noncoding regions). DNA
fingerprinting focuses on these regions. These regions include stretches
that repeat. Each person’s DNA differs in the numbers of copies of the
repeated sequences.
The difference in the number of repeats are found by separating the DNA
fragments with gel electrophoresis.
The pattern of DNA fragments on a gel represents the uniqueness of a
person’s DNA (“fingerprint”).
Learning Check
1. The diagram below represents DNA
fingerprints which are the results of gel
electrophoresis done on several DNA
samples found as a crime scene.
Which suspect is linked to the crime scene
by this DNA analysis? Do you think any of
the suspects are related?
Suspect C
Related B and C
2. Each fragment of DNA is marked with a
letter. A child MUST get each of its
fragments from at least one of it’s
parents. (this is all the same 3 people)
Is the alleged father the child’s father?
Yes possibly.
Learning Check
Did the following puppies come from the indicated
parents?
Yes those parents COULD have produced this puppy.
Puppy 2 did not come from these parents
Genetic Engineering
AKA genetic modification (GM)
It relies on cloning of genes (segments of DNA). In some cases, scientists insert cloned genes from one
organism into a different organism. This changing of an organism’s DNA to give the organism new traits is
called genetic engineering.
It is based on the use of recombinant DNA technology. Recombinant DNA is DNA that contains genes from
more than one organism.
First GMO was in 1973– bacteria. Bacteria are commonly used because they have tiny rings of DNA—
PLASMIDS.
•
•
Plasmids are used as vectors (vehicles) in genetic engineering
Gene to be replicated is inserted into plasmid ( often antibiotics)
PCR (Polymerase Chain Reaction)
A sample of DNA is too small to work with. A specific DNA sequence must be
copied, or amplified, to produce a sample that is large enough to study. PCR
(Polymerase Chain Reaction) is a technology that uses DNA polymerases to
produce millions and even billions of copies of a specific DNA sequence in just a
few hours.
***The amplification of recombinant plasmids occurs by PCR***
How are replication and PCR similar? Different? Explain.
They both copy DNA. Replication copies entire DNA strand, but PCR only copies a
section of DNA over and over again.
Many human genetic diseases are caused by recessive alleles of genes. How might
PCR be important in the diagnosis of these illnesses?
You can design primers that will detect these alleles and you could find out if a
person has that specific disease with in hours, just by collecting a small DNA
sample
Uses of Genetic Engineering
The cow = GM cow that produces milk without lactose = no
allergies, milk also has more proteins and vitamins
Some species have been GM to produce less fat = leaner
meat
GloFish—available at a Walmart near you, glow under black
light. DNA from jellyfish inserted into fish—fish make
proteins that glow
Potential risks : Government regulation. Creation of superbug etc. GMO plants that make protein to kill insects, insects
become resistant etc.
Genetic Engineering – Cloning
Producing genetically IDENTICAL organisms
Occurs in nature when plants, bacteria etc. reproduce asexually (by
mitosis—NO partner) assuming no mutations occur.
Ex. Strawberries
Ex. Bacteria (binary fission)
Dolly the sheep (1996) - First mammal to be cloned from a somatic (BODY)
cell (taken from the udder)
Other species cloned: horses, bulls, cows, pigs, and mice.
Steps to make Dolly
• Unfertilized egg from black faced
sheep (ewe) removed and
enucleated (nucleus taken out)
Surrogate
• Body cell with the nucleus (DNA) is
donated by the udder of a whitefaced sheep Nuclear Donor with
desired genes
• The body cell with the nucleus (DNA)
is placed next to the empty egg.
Electric shock fuses the cells.
• Zygote grown in a lab until it was a
blastocyst
• Implanted into surrogate ewe.
• Clone!! Identical to Donor sheep
• What color face did Dolly have?
White Why? DNA (nucleus) was
donated by the white-faced sheep.
Empty Egg cell
with vital
components
In the cytoplasm.
1/2 the number of
chromosomes
Body=somatic cells
with desired GENES
Have full set of
chromosomes
Shocked to FUSE
IMPLANTATION
White-faced CLONE
Learning Check
Tissue taken from a black mouse was enucleated. The resulting nuclei were
then put inside the enucleated egg from a white mouse. What color would
the baby mice be?
The mice would NOT resemble the white mouse but would be identical to
the black mouse (nuclear donor)
Monozygotic (identical) twins are formed from a fertilized embryo splitting
into 2 separate masses during development. Is this the same as cloning?
No, when twins form they are splitting a developing organism. Cloning
involves placing DNA from another organism into an empty egg
What is cloning?
It involves placing DNA (nucleus) from a body cell of another organism,
the nuclear donor, into an empty egg cell.
Genetic Engineering
Types of Controlled BREEDING
A. Selective Breeding (Artificial Breeding)
When humans have selected desirable traits and mated organisms in an attempt to increase
the trait in a population (controlled sexual reproduction).
Most domestic animals. Ex. Dogs
Ex: Corn
What effect does selective breeding have on a population’s variation? It will usually
decrease variation because we eliminate some variations in favor of an extreme
Genetic Engineering
Types of Controlled BREEDING
B. Inbreeding
Mating of genetically similar pairs with similar characteristics
(closely related—immediate family). Results in homozygosity,
which can increase the chances for an offspring being
affected by a recessive condition.
At one time common in royalty. Ex. Hasburg chin
Why is inbreeding prohibited in the AKC - purebred dog
Registry (to some extent)? It decreases the vitality (health) of
the dogs by making them more susceptible to genetic
disorders
Hybridization
Offspring resulting from the interbreeding of two different (but closely
related) species to bring the best traits of both organisms.
Creating hybrid plants is different than creating hybrid animals.
Animal hybrids usually have reduced vigor– this is often attributed to a
mismatch of the chromosome number and results in sterility if
chromosome number is odd.
Ex. Donkey x Horse
Donkey= 62 chromosomes X Horse= 64 chromosomes = Mule (63) Sterile
Many crops today are hybrids. Hybrid plants are usually stronger and
healthier, with higher resistance, productivity and lifelongness: Rice, Chili,
Tomato.