Disorders and Genetic
Pictures of chromosomes, cut out and
placed in order of size and location of
centromere. Placed in homologous pairs.
Normal male karyotype
Can show chromosomal
Down Syndrome: Trisomy 21
retardation, many physical differences
These disorders result from
Failure of chromosomes to separate
normally during meiosis
Eggs or sperm get one too many chromosomes
or one too few.
Down syndrome has one extra #21
Klinefelter has one extra X chromosome
Turner has one too few
only one X
Other Human Disorders
Sickle Cell Anemia
Found most often among people of African
Blood cells sickle (change shape) when
deprived (exertion, increase in altitude)
Causes sickle cell event
pain and immobility
and death of tissue ( dangerous if in organ)
hospitalization and oxygen
Carriers are resistant to malaria
Tay Sachs Disease
Found most often among Jews of
Child born appearing normal, but fat builds
up in brain and child dies by age 5
No treatment, no cure
Symptoms do not appear until age 30
Death takes about 5
No treatment, no cure
but there is a test to see
if you have it before symptoms begin
Results in mental impairment and
uncontrollable spastic movements
Person can’t breakdown phenylalanine (one
of the 20 amino acids)
OK when born, but if phenylalanine not
restricted by diet, mental retardation will
result, getting worse the longer
phenylalanine is in the diet.
Diet prevents PKU
Chromosome fragment breaks off and is
Cri du chat syndrome
and many physical problems
removes a little amniotic
fluid from around baby
fluid is then tested
for abnormal proteins and the cell in it can
Risk of miscarriage
Chorionic Villus Sampling
Take a piece of the chorionic villus from the
it is made of baby cells
as in amniocentesis
Can be done earlier than amniocentesis
Risk of miscarriage
Has been linked to deformed fingers
Only truly noninvasive test
supply a view of the baby
can see many
Totally risk free
Once a prenatal diagnosis of a genetic
disorder is made, what are the parents to
Do nothing and give birth to child with disorder
Who should make the decision?
What should enter into making the decision?
educates the parents about the disorder,
tells them of their options without influencing
and tells them of the consequences of each
We can manipulate DNA and genes to alter
organisms or make them produce a product
DNA from two
different sources joined together.
Cut the DNA and the plasmid using the
same restriction enzyme (these enzymes
recognize the same base sequences.
Insert the foreign DNA into the plasmid.
Replace the plasmid into the bacterium
Allow the bacterium to reproduce
future generations have the new DNA
Collect the product
it might be insulin or
growth hormone, or some other molecule.
Cloning and the Wider World
of Biotechnology (Section 15.3)
Definition of Cloning
To make an
exact genetic copy of; can be a gene, a
cell, or an entire organism.
How Dolly was cloned
In 1997 by researcher Ian Wilmut and colleagues
at PPL Therapeutics.
Figure 15.6 is Animated in the Chapter 15 Media
A cell was taken from udder of adult sheep
and grown in culture in a laboratory to create
many daughter cells.
An egg was taken from another sheep, and its
nucleus was removed.
The udder cell and the
denucleated egg were fused by
electricity, stimulating the egg
to develop as if it had been
fertilized using the diploid
udder cell nucleus instead of
the sperm and egg nuclei.
The embryo that developed
was implanted into a surrogate
mother sheep, and was born as
Dolly, with the exact DNA from
the original udder cell.
Benefits of cloning
Wilmut and colleagues were not
just interested in cloning on its own; instead, they
wanted to combine cloning with recombinant DNA
technology for a variety of benefits:
Creating livestock that contain human genes needed
to treat genetic disorders like hemophilia (Factor
Creating livestock to serve as organ donors, or
Polymerase Chain Reaction
Used to “amplify”
make large amounts of a specific
piece of DNA from a very small sample.
Technique: Figure 15.7
Heat a starting quantity of DNA to separate the
Add a collection of all four nucleotides, and DNA
polymerase to copy the DNA, and some primers,
and cool the sample.
Primers are short sections of DNA that are
complementary to the region on both ends of the
DNA that you wish to copy. Primers act as signals
to tell DNA polymerase where to copy. As the
solution cools, they stick to the DNA you wish to
copy and allow polymerase to do its job.
Heating the sample again unwinds the new
duplicated strands; cooling again allows more
primers to bind. If you repeat this as a cycle, you
can make millions of copies of the original DNA.
(Interactive Activity 2)
Visualizing DNA Sequences (Section 15.5)
So many bases, it is best to visualize them all in some organized
Restriction enzymes can be used to cut the chromosomes
from many cells into manageable pieces.
There will be a collection of copies of fragment 1, which is a
different size than fragment 2, and so on.
The pieces can be ordered according to size using gel
electrophoresis (moving the fragments in an electric field
through a gel matrix). Larger pieces are more easily
retarded by holes in the gel, so they travel less than smaller
pieces: Figure 15.8
Animation: DNA Tool kit from Chapter 15 Media Lab:
Dyes that bind DNA can then be used to visualize the
fragments as bands that can be compared to
reference DNA fragments of known size.
Characterizing a stretch of DNA by the order of
As, Gs, Cs, and Ts.
Regularly performed by machine.
“DNA in the Courtroom”
Use of VNTRs (variable number of tandem
repeats; different individuals have different
numbers of repetitive stretches of DNA, for
example, GGAGG). One individual might have 6,
VNTRs can be analyzed by gel electrophoresis,
creating a banding pattern specific to each
like a bar code (Interactive Activity 3)
The Human Genome Project
Massive undertaking to locate and
catalogue every bit of genetic information in
the human genome.
Budget of $300 million in 1998
Knowing all the sequence is not the same
as knowing what all the genes do,
Just a good reference point to start.
(Interactive Activity 4)
Uses of Biotechnology (Section 15.7)
Biopharmaceuticals: Table 15.1
from recombinant DNA technology
Human Gene Transfer
gene therapy, replacing
defective gene with a working one to treat genetic
Insert gene into vectors which will allow it to be
added to human cells.
Best cells to infect are stem cells.
specificity, triggering immune
response, keeping cells producing the protein
Biotechnology and food:
Boost milk production 25 percent in cows with
bovine growth hormone made in bacteria.
growing salmon: Figure 15.10
Biotechnology and food:
Genetically altered crops
First came to market in
1994, by 1998 there were 45 million acres in
production. Two categories of genetic alterations:
Added genes for herbicide resistance
Added genes for killing pests: Figure 15.11
Bt toxin). Concerns
about insects building resistance, plants
passing genes to wild relatives, or
inadvertently killing off beneficial insects like
butterflies. (Interactive Activity 5)
Benefits of DNA sequence knowledge for
Ethical Questions in Biotechnology
Five percent of the Human Genome Project is
devoted to ethical ramifications
Ethical to modify humans, how far should we go?
Chickens without legs or eyes?
Will biotech produce new harmful organisms?
Are biotech diagnoses running far ahead of
Genetic discrimination? Who can have access to