Download Biology Chapter 13 DNA Technology and Genomics 5-20

DNA Technology and Genomics
Human Genome Project
 Started in 1990
 Goal was to map the human genome by determining
the sequence of nucleotides in human DNA.
o Information available on the Internet for people
to access.
 Completed around 2003
 Benefits:
o Embryonic development
o Evolution
o Disease diagnosis and treatment
o Prevent heart disease, allergies, diabetes,
schizophrenia, alcoholism, Alzheimer’s and
cancer
 Humans have roughly 25,000 genes – fewer than
expected
o A human gene might code for more than one
polypeptide utilizing alternative splicing.
 97% is noncoding DNA
o Gene control sequences – promoters and
enhancers
o Introns
o Noncoding regions between genes
o Telomeres – repetitive ends on DNA
Download the human genome
Human Genome Project:
 After the human genome was sequenced, scientists
started on scientifically valuable organisms
o Over 180 eukaryotic species
 Yeast
*
 Worm
*
 Mustard plant
*
 Fruit fly
*
 White lab mice
*
 Mosquito
Dog
Rat
Chicken
Frog
Neanderthal
o Around 4000 bacteria (Archaea and Eubacteria)
Eukaryotic Genomes
 Largest – rare Japanese flower – 149 billion base
pairs (50X the size of the human genome)
o Human – 3 billion base pairs
 Smallest – mammalian parasite – 2.25 million base
pairs
Comparisons of genome sequences from different species
allows us to evaluate evolutionary relationships
o More similar genome = more closely related
The success of genomics has focused attention on proteins
 Full set of proteins – proteomes
o Proteomics – Studying the whole set of proteins
and their interactions.
Restriction Enzymes – Biological scissors
An enzyme that cuts
DNA at or near specific
recognition nucleotide
sequences known as
restriction sites.
Gel Electrophoresis and DNA Sorting
Gel electrophoresis is a technique that uses a gel (jellylike
substance) to sort DNA/RNA/Proteins based on their size
or electrical charge.
Steps:
 DNA samples are exposed to the same restriction
enzymes
 DNA samples are loaded into different wells
o Each sample contains DNA fragments of
different lengths
 An electrical current is applied (negative at the top,
positive at the bottom)
 DNA has a strong negative charge so it moves towards
the positive end (bottom)
 Smaller fragments move through the spaces in the gel
faster than longer fragments
Gel electrophoresis allows numerous samples to be
compared based on their number of fragments and fragment
length
 Must pick variable region (introns)
Since your DNA is unique to you (except identical twins*),
your number of fragments and their lengths will be unique
as well – DNA fingerprint
This technique can be used to compare a suspect’s DNA to
samples collected at a crime scene
This technique can be used to determine if a person is
carrying a harmful allele
 After gel is produced, use DNA probe complementary
to the gene in question to determine if the gene is
present
o One or more fragments will be detected
http://www.youtube.com/watch?v=UYAGhRi30oM
https://www.youtube.com/watch?v=mN5IvS96wNk
Gene Probes
How do scientists find the right DNA fragment to insert
into the plasmid or make a fragment more unique?
Scientists can use their understanding of complementary
base pairing if a gene sequence or partial sequence is
known.
 Use radioactive isotopes to produce a radioactive
complementary strand to the gene called a nucleic acid
probe
o Gene with TAGGCT
o Probe has ATCCGA
 Use heat or chemicals to separate the DNA then mix
with the probe
Stem Cells
A zygote divides by “Mitosis” to produce a multicellular
embryo made of stem cells – undifferentiated cells.
 The cells in the first few rounds of division are
Totipotent – they can differentiate into any type of
cell.
As the embryo develops further, the cells begin to
specialize and lose their ability to differentiate into any
type of cells. These cells are Pluripotent. Also known as
embryonic stem cells.
 These cells can become any body cell, but not all cells
of the original embryo.
Adult stem cells produce new cells for tissues that need
continual renewal. These cells are Multipotent. They can
produce a limited number of cell types.
 Skin
 Blood cells
Animal Cloning
Cloning History:
 1979 – First genetically identical mice produced by
embryo splitting.
 Clones produced by nuclear transfer of embryo into an
emptied nucleus (cows, sheep and chickens)
 1996 – First mammal clone from a body cell taken
from an adult animal (sheep – Dolly)
C
 1998 – Cloned eight calves from a single cow
Somatic cell cloned animals:
Sheep
Cattle
Cat
Deer
Mule
Ox
Rabbit
Rat
Embryo splitting: Rhesus monkey
Dog
Horse
A
B
C
Basic steps:
1. A diploid nucleus is removed from sheep A.
2. The nucleus is removed from an egg from sheep B.
3. The nucleus from sheep A is transferred to the empty
egg from sheep B.
4. Electricity is used to stimulate mitosis.
5. The multicellular embryo is transferred into sheep C
for gestation.
6. Sheep C gives birth to the lamb.
To which sheep is the lamb identical (a clone)?
Would you pay $100,000 to clone a pet?
Chimera
Injecting cells from one species into the embryo of another
creates mixtures called chimeras. From left to right: an
ordinary mouse, a mouse that’s partly rat, a rat that’s partly
mouse, a white rat.
Chimeras are defined as organisms composed of cells or
genes obtained from two or more different organisms or
species.
Recombinant DNA Technology
Recombinant DNA Technology – Laboratory techniques
for combining genes from different sources (same species
or different) into a single DNA molecule.
 Used to alter the genetics of organisms to make them
more useful to humans
o Use bacteria as chemical factories to produce
human proteins.
o Make plants more drought resistant
o Increase the growth rate of plants/animals
o Make animals glow in the dark
 Heavily dependent on bacteria. Why?
o Plasmid – small, circular double stranded DNA
molecules
 Carry few genes
 Replicate on their own
 Great for gene cloning – multiple
copies of gene-carrying piece of DNA
 Are passed from bacterial cell to cell
 Great for recombinant DNA – DNA in
which genes from two different sources are
combined into the same DNA molecule
How do we get the “gene of interest” out of the original
chromosome/DNA and into the bacterial plasmid?
Use Restriction Enzymes
Restriction Enzymes and “Sticky Ends”
Restriction enzymes are the cutting tools used to remove a
gene from one molecule of DNA and to open the new DNA
molecule for “pasting”.
 Original use was to protect bacteria from foreign DNA
that enters their cell.
 Restriction enzymes recognize specific DNA
sequences and cut the DNA at points within the
sequence.
o Need cuts that leave jagged, “sticky ends”
 Between which nucleotides was the molecule cut?
A and C
How can a new gene be inserted into the broken DNA
molecule?
Cut it out with the same restriction enzyme.
It will have complementary “sticky ends”
allowing base pairing.
What enzyme do you think is used to covalently bond the
sugars/phosphates to complete the DNA backbone?
DNA ligase
The final result is a recombinant DNA molecule
Restriction Enzymes
http://www.dnalc.org/resources/animations/restriction.html
https://www.youtube.com/watch?v=lWXryzgRces
Bacteria with recombinant DNA plasmids can be used as
biological factories to clone useful genes for humans.
Ex. Insulin – taken for diabetes
In the past, people used insulin produced by other animals.
 Similar to human insulin
o Rejection/allergic reactions possible
Now we inject human genes into bacteria and have them
make human insulin.
 Identical to insulin produce by humans
o No rejection/reaction
What is used to cut the plasmid?
Restriction Enzymes
How many times is the plasmid cut?
What is used to cut the DNA?
1
The same restriction
enzyme
How many times is the human DNA cut (minimum)?
2
What would you do?
1. You are a tomato farmer whose crops are threatened by a
persistent species of beetle. Each year, you spend large
sums of money for pesticides to protect your crops. A
biotechnology company introduces a new strain of tomato
plant that produces a natural pesticide, making it resistant
to the beetle. By switching to this new strain, you could
avoid both the beetle and the chemical pesticides
traditionally needed to fight it.
2. As a family physician, you often treat children who
suffer from infectious diseases that could easily be
prevented through vaccination. But the parents of many of
your patients cannot afford the cost of vaccinations. You
hear of a new approach that would reduce the cost to a
fraction of its current price: genetically modified fruits and
vegetables that contain various vaccines. By simply eating
a banana, a child could be protected against disease—
without getting a shot!
3. You are the leader of a developing nation. Hunger is a
problem among your citizens: the salty coastal wetlands of
your country can't support the growth of needed crops, and
your slow economy can't support importing enough food
for everyone. A biotechnology company has genetically
modified a rice plant that can thrive in salt water, providing
your nation with the opportunity to feed its citizens while
bolstering its economy.
Genetically Modified Organisms (GMO’s) have acquired
one or more genes from artificial means rather than by
traditional breeding methods. A term usually associated
with commercially available foods.
 Grow faster
 Produce greater fruit
 Improved nutritional value
 Drought resistance
 Chemical/herbicide resistance
 Cold weather tolerance
If the newly acquired gene is from a different species the
GMO is called a transgenic organism.
Concerns are being raised about long-term consequences to
human health and the environment, as well as access to
resources.





Allergens
Organ damage
Resistance transferred to pest species
Harm nontarget species
Affordable seeds
SciShow
Bill Nye
Are GMOs Good or Bad?
Organisms that have been genetically engineered:
In 2007, South
Korean
scientists
altered a cat’s
DNA to make
it glow in the
dark and then
took that DNA
and cloned
other cats from
it, creating a
set of fluffy,
fluorescent
felines.
Scientists have recently taken the gene that programs
poison in scorpion tails and combined it with cabbage. Why
would they want to create venomous cabbage? To limit
pesticide use while still preventing caterpillars from
damaging cabbage crops. These genetically modified
cabbages produce scorpion poison that kills caterpillars
when they bite leaves — but the toxin is modified so it isn’t
harmful to humans.
Strong, flexible spider silk is one of the most valuable
materials in nature, and it could be used to make an array of
products — from artificial ligaments to parachute cords —
if we could just produce it on a commercial scale. In 2000,
Nexia Biotechnologies announced it had the answer: a goat
that produced spiders’ web protein in its milk.
Researchers inserted a spiders’ dragline silk gene into the
goats’ DNA in such a way that the goats would make the
silk protein only in their milk. This “silk milk” could then
be used to manufacture a web-like material called Biosteel
The Enviropig, or “Frankenswine,” as critics call it, is a pig
that’s been genetically altered to better digest and process
phosphorus. Pig manure is high in phytate, a form of
phosphorus, so when farmers use the manure as fertilizer,
the chemical enters the watershed and causes algae blooms
that deplete oxygen in the water and kill marine life.
So scientists added an E. Coli bacteria and mouse DNA to a
pig embryo. This modification decreases a pig’s
phosphorous output by as much as 70 percent — making
the pig more environmentally friendly.
Starlight Avatar