So what is gene therapy? - OoCities

whooshdisguisingBiotechnology

Dec 14, 2012 (4 years and 6 months ago)

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Reproduction and

Fetal Technology

Annabel Barajas

Tamari Zeigler

Thomas Ji

Jared Salisbury

Nathan Vasquez

Genetic Engineering and Gene
Therapy




Both

genetic

engineering

and

gene

therapy

have

the

same

basic

premise
:

of

having

an

introduction

of

a

specific

new

genetic

material

into

an

organism’s

genome


Some General Genetic Facts



A single chromosome contains about 1000
genes


Humans have approximately 30,000 different
kinds of genes spread out over the 46
chromosomes


Humans get one complete set of genes from
each parent

More General Facts on Genes
and Disease Relationship’s



An abnormal gene is called a mutation


Abnormal genes can cause disease or , more
commonly, can change your risk of
developing a disease


Most common diseases are caused by a
mixture of environmental, dietary and genetic
factors


In a normal cell , it is common for many
genes to be “ silent” (not expressed)

So what is genetic
engineering?



Genetic engineering refers to the deliberate
design of an entire organism. The process
involves altering the genetic material of a single
cell in a very small developing embryo, which
then develops into an entire organism, with the
altered genetic material in every cell.


The basic strategy is to place the new genetic
material into the cell, and use the cell’s natural
machinery to integrate this material into the
genome

There are several ways to conduct
the process of genetic engineering



One way is through horizontal gene transfer. Horizontal
gene transfer refers to the transfer of genes or genetic
material directly from one individual to another by processes
similar to infection.



"Somatic"

genetic engineering is genetic engineering that
targets the genes in specific organs and tissues of the body
of a single existing person without affecting genes in their
eggs or sperm. Somatic gene transfer experiments are
currently undergoing clinical trials, with mixed results to
date.


"Germline"

genetic engineering is genetic engineering that
targets the genes in eggs, sperm, or very early embryos. The
alterations affect every cell in the body of the resulting
individual, and are passed on to all future generations.

The dangers, moral and ethical questions
raised by genetic engineering



Genetic engineering is inherently hazardous, because
it depends on designing artificial vectors to cross all
species barriers, greatly increasing the potential for
generating new viral and bacterial pathogens by
horizontal gene transfer and recombination


Genetic engineering poses unprecedented ethical and
social concerns, as well as serious challenges to the
environment, human health, animal welfare, and the
future of agriculture


Also concerns about the consequences of altering a
few select genes, since genes interact in very
complex ways, and we may not be able to predict all
the consequences of any specific manipulation.

So what is gene therapy? And
how does it work?



Gene therapy is an experimental technique that uses
genes to treat or prevent disease


In the future, this technique may allow doctors to
treat a disorder by inserting a gene into a patient's
cells instead of using drugs or surgery


Gene therapy is designed to introduce genetic
material into cells to compensate for abnormal genes
or to make a beneficial protein


If a mutated gene causes a necessary protein to be
faulty or missing, gene therapy may be able to
introduce a normal copy of the gene to restore the
function of the protein.

A Diagram showing the process



A
genome
-

is the totality of the genetic material of a
cell or organism


Vector

-

A vector is a small piece of DNA used to
carry a gene of interest. Besides the gene being
studied, a vector may contain elements which are
used to help the gene integrate into a genome


Recombination

-

The process in which strands of
DNA are cut open and rejoined. This is done by a
complex of proteins called DNA recombinase.
Recombination can be used to integrate the DNA from
a vector into an organism's genome

Is gene therapy safe?



Gene therapy is under study to determine whether it
could be used to treat disease


Current research is evaluating the safety of gene
therapy; future studies will test whether it is an
effective treatment option. Several studies have
already shown that this approach can have very
serious health risks, such as toxicity, inflammation,
and cancer


Because the techniques are relatively new, some of
the risks may be unpredictable; however, medical
researchers, institutions, and regulatory agencies are
working to ensure that gene therapy research is as
safe as possible.

What are the ethical issues
surrounding gene therapy?



How can "good" and "bad" uses of gene therapy be distinguished?


Who decides which traits are normal and which constitute a disability or
disorder?


Will the high costs of gene therapy make it available only to the wealthy?


Could the widespread use of gene therapy make society less accepting of people
who are different?


Should people be allowed to use gene therapy to enhance basic human traits
such as height, intelligence, or athletic ability?


The idea of germline gene therapy is controversial. While it could spare future
generations in a family from having a particular genetic disorder, it might affect
the development of a fetus in unexpected ways or have long
-
term side effects
that are not yet known.


Because people who would be affected by germline gene therapy are not yet
born, they can't choose whether to have the treatment. Because of these ethical
concerns, the U.S. Government does not allow federal funds to be used for
research on germline gene therapy in people

Artificial Insemination
-

Intrauterine Insemination (IUI)


“Granddaddy” of fertility treatments. It dates back to the
early 1900’s.


“First Line” treatment used before any other Assisted
Reproductive Technologies (ART’s) are used.


It is used when an unexplained fertility problem is
present.


Very simple procedure: only healthy sperm, and delivery
device, and a female to receive the sperm are needed.


Much less invasive than other ART procedures

Process


Female usually undergoes a cycle (at
least one week) of Clomid or FSH to
stimulate development of eggs.


Once ovulation occurs a sample of
sperm is collected either from father or
from a sperm bank.


The sperm is then “washed.” Which
concentrates the hardiest sperm and
removes any potential antigens that
may cause allergic reactions in the
female.


The “washed” sperm in delivered
directly to the uterus using a catheter.


Two weeks later a simple over the
counter pregnancy test will determine
if the female is pregnant or not.

Advantages



-
If the female has a sperm allergy


-
If the male has a low sperm count or poor sperm
mobility


-
It allows fertilization to occur naturally inside the body
unlike other ART’s


-
If antisperm anti bodies are present in vagina they are
bypassed using catheter


-
No father is needed, can acquire sperm from sperm
banks.


-
Cost: average ranges between $300
-
$700 per cycle

Disadvantages



-
Most couples only have a 5%
-
25%
success rate using IUI


-
May have to repeat process several times
to achieve pregnancy


-
Weak children may be a result due to the
fact that weaker sperm have a chance to


reach the egg.

Human Cloning



Cloning is the
reproduction of an
individual single cell
taken from a donor or
parent.

Somatic Cell Nuclear Transfer
(Therapeutic Cloning)


Egg from female donor is
taken and the nucleus is
removed creating an
enucleated egg.


A somatic cell (non
-
reproductive cell) is then fused
together with the enucleated
egg producing an embryo.


The embryo is implanted into
the surrogate mother using in
vitro fertilization.


If it is a success, nine months
later an exact clone of the
somatic cell donor is created.


After hundreds of
attempts Dolly the
sheep was created.
After a short life of 6
years she was put to
sleep after suffering
from a progressive
lung disease.

Questions raised:


Scientists are concerned that the clone will
have cells that are the same age as the
donor cells.


Will parents try to live the life they weren’t
able to through their exact clone?


Will knowing that they are not only a child
but also a sister/brother of parents
emotionally damage the clone?

Assisted Reproductive
Technology (ART)


Most ART procedures are recommended in cases of ovulation
problems, blocked fallopian tubes, low sperm count in partner, and
if other treatment method are unsuccessful.


Doctor prescribes fertility drugs prior to ART procedures to stimulate
ovaries to develop several mature eggs for fertilization. The doctor
will then monitor blood hormone levels to detect when the eggs are
mature.


Since the sperm is put in the direct vicinity of the eggs in a dish it is
possible to achieve fertilization with a lower than average sperm
count.


Since more than one embryo may be implanted there is a higher
possibility of multiple birth pregnancies than with natural child birth.


In Vitro Fertilization (IVF)


A procedure in which a sperm and oocyte are combined in a
laboratory dish and implanted in the uterus.


IVF is the most common ART procedure used, accounting for more
than 70% of ART procedures.


In the past eggs were retrieved using a laparoscopy procedure;
however, due to advancements in technology eggs are now
retrieved vaginally with the use of an ultrasound to determine the
location of the eggs.


After about 2
-
5 days the fertilized eggs form an embryo and are
then implanted in the uterus, using a catheter, to develop naturally.


Treatment takes about six weeks to complete.

Gamete Intrafallopian Transfer (GIFT)


A procedure similar to IVF but in GIFT the eggs and
sperm are transferred into the fallopian tubes
immediately after the two are mixed. There is no time
given for the eggs to be fertilized before the transfer.


GIFT accounts for about 2 percent of ART procedures.


The egg and sperm mixture are implanted in the fallopian tubes
using a laparoscopy procedure.


One cycle of GIFT takes about six weeks.


GIFT is the closest ART procedure to natural childbirth.


Zygote Intrafallopian Transfer (ZIFT)


Similar to GIFT except the egg is fertilized
before it is placed in the fallopian tubes.


ZIFT also referred to as tubal embryo transfer (TET).


It is different from IVF since the embryo is placed in
the fallopian tubes instead of the uterus.


Only accounts for one percent of ART procedures.


Zygotes are transplanted about one day after
fertilization.


If the treatment is successful the zygote will travel to
the uterus and implant itself, where it will develop.


Frozen Embryo Transfer (FET)


Frozen embryos can be frozen after 24
-
72 hours
in a culture.


Frozen embryos can be stored for several years.


Embryos will be thawed and replaced in the
uterus once ovulation is identified by a doctor or
when the endometrium is thick enough.


Not all embryos survive the freezing, storage,
and thawing processes.


Thawed embryos are implanted in the uterus
using a catheter.


Intracytoplasmic Sperm
Injection (ICSI)


This procedure was introduced in 1982, and continues to
be a popular treatment in treating male infertility.


ICSI is prescribed in cases of low sperm count, missing vas
deferens, or irreversible vasectomy.


The male provides the doctor with a sperm sample by
ejaculation. However, if there is not enough sperm in ejaculate
the doctor may remove sperm from the testicles using a needle
or perform a biopsy of the testicular tissue.


There is concern for the long term health and development of
children conceived by ICSI since it enables weaker sperm to
fertilize eggs.


Surrogate Motherhood


Surrogate mothers are women who carry a child for a mother who
is unable to conceive with the intention of giving the child up once it
is born.


Also known as ersatz mothers


Surrogate pregnancies are conceived through artificial insemination.


In gestational surrogacy the surrogate mother is implanted with the real
parent’s embryo using an IVF procedure.


Some gay male couples use surrogate mothers to have children that are
biologically related to at least one of the partners.


Surrogate mothers usually receive compensation for carrying the child.


There are many ethical and legal concerned with this process since
some surrogate mothers grow attached to the fetus and sue for custody
of the child they carried. The most publicized case is that of Baby M.


Storage of gametes and embryos


Sperm cryopreservation &

embryo cryopreservation


Gamete is a sex cell containing the genetic
material necessary for reproduction


Embryo is the early form of life in the
uterus between the stages of blastocyst
and fetus


Cryopreservation is a process to store
gametes or embryos by freezing them at
low temperatures


Sperm cryopreservation &

Embryo cryopreservation


Collect semen from self
-
masturbation


More portions of semen can be
cryopreserved. This so
-
called “test thaws”
will be warmed up to verify success


Retrieve egg under ultrasound guidance


Embryo can be frozen at any stage


Both sperm and embryo are stored in
liquid nitrogen, around
-
196C


Benefits from Sperm &

Embryo cryopreservation


People facing surgery, radiation therapy or
chemotherapy for cancer or other medical operations
that can make them sterile


If a male partner is expected to be away, cryopreserved
sperm can be used in time for optimal insemination


Cryopreservation can help people with internal problem
such as cervical stenosis


Frozen sperm or embryos can be donated to infertile
couples


Lesbian couples who wants a child from cryopreservation
method if they don’t desire sexual relationship with a
male partner


Problems of Sperm &

Embryo Cryopreservation


Not all sperms and embryos can survive the
freezing and thawing process


Pregnancy rate using frozen sperm or embryo
may have lower chance compared to using fresh
sperm or embryo


No apparent birth defects from using frozen
-
thawed sperm but it is not sure whether
problems will not appear in the future


Chance of possible infection with a bacteria or
virus


Choices and Moral Issues


Couples have choices to:


continue to store them


arrange for the transfer treatment cycle before expiration


discard them by interfering during the thawing process


donate them to approved research facility or to infertile couple.


Most countries have different policies on how long sperm & embryo
can be stored, United Kingdom is 10 years


Moral issues surrounding the cryopreservation process:


the fate of cryopreserved sperm or embryo on the death of couple who
preserved them


ownership of the sperm or embryos if the couple separates, safety of
sperm & embryo cryopreservation



a possible detrimental effect on the outcome of cryopreserved sperm &
embryo transfer and possible increase in fetal abnormalities after long
period of cryopreservation.


Fertility Drug Treatments

WHAT ARE THEY FOR?


Women


Treat irregular ovulation


Help those who do not ovulate at all


Polycystic ovarian syndrome (PCOS)


Men with hormonal imbalances


Low sperm count


Poor sperm quality or motility


Primary hypogonadotrophic hypogonadism

TYPES


Clomiphene


Oral Pill


Gondotropins


Shot


Bromocriptine


Oral or Vaginal Pill

HOW LONG IS THE
TREATMENT?


Clomiphene
-

You start 3 to 5 days into
your cycle and continue for about 5 days


Gonadotrophins
-

7 to 12 days each month


Bromocriptine
-

2 to 3 times a day until
you get pregnant

POSSIBLE SIDE EFFECTS


Bloating


Fluid retention


Weight gain


Nausea


Dizziness


Fatigue


Diarrhea


headaches


Abdominal tenderness


Stomach pain


Brest tenderness


Blurred vision


Irritability


Depression

CAN THEY CAUSE CANCER?



Beliefs



1999 & 2000 studies

SUCCESS RATES

It varies by treatment:


Clomiphene
-

80 percent ovulate of this 40 percent get
pregnant


Gonadotrophins
-

20 to 60 percent conceive


Bromocriptine
-

90 percent ovulate, 65 to 85 percent get
pregnant


COST


Clomiphene
-

$50 on one cycle of Clomid


Gonadotrophins
-

$2,000 to $5,000 per cycle


Bromocriptine
-

$75 to $112 on one cycle


* This is in the United States.

SEX SELECTION

QUICK FACTS


Males and Females


Carry 23 pairs of chromosomes


Difference between males and females


Lies in the 23rd chromosome


Girls have two X chromosomes


Boys have one X and one Y chromosome

IDENTIFYING THE SEX


Before implanting the embryo into the
mother, a fertility doctor stains the
chromosomes.


The x chromosome will be a different color
than the Y chromosome.


Under the microscope, the doctor can
easily tell whether the embryo is male or
female.

THREE MAIN TECHNIQUES

OF SEX SELECTION


Sperm Sorting Before Conception



Preimplantation Genetic Diagnosis (PGD)



Microsort

SPERM SORTING BEFORE
CONCEPTION


Sperm sorting can be carried out either by
putting live sperm in a dense liquid and
spinning it in a centrifuge to separate
sperm carrying the X chromosome and
those carrying the Y chromosome.

PRE
-
IMPLANTATION GENETIC
DIAGNOSIS


This procedure is carried out before the
embryo is transferred into the woman.


A cell is removed from the embryo for
genetic testing to detect X or Y
chromosomes.


It is more controversial technique than
sperm sorting because it involves
embryos.

MICROSORT


This procedures involves using a
fluorescent dye which binds to DNA in
chromosomes in the semen sample,
allowing the sperm to be separated using
a laser.