Download Human intervention in evolution Part 2 2012

Human Intervention in
Evolution
Chapter 16 – Part 2
Transferring genes between
species
 The universal nature of
DNA allows scientists to be
able to manipulate DNA
between species.
 As a result scientists can
transfer genes from one
organism into another
organism.
Gene transfer between
species
 As a result of DNA being universal among all living things, it has
allowed scientists to transfer whole genes between species.
 Genetic engineering has allowed genes to be transferred
between different species.
 Any organism that has a foreign gene, or foreign piece of DNA is
said to be a transgenic organism (TGO).
 If the cell that is receiving the foreign DNA is a prokaryotic cell,
then it is said the gene is transformed.
 If the cell that is receiving the foreign DNA is a eukaryotic cell,
then it is said the gene is transfected.
Techniques for gene transfer
 There are different techniques that can be used to
introduce genes into a cell.
 DNA can be micro-injected into a host cell
 The DNA can be carried to the target cell in a retrovirus
or adenovirus.
 An electric pulse can be used.
 Using a ‘gene gun’
Cloned transgenic animals
 Once a desired gene is taken up by the embryo of a
particular organism, it is then cloned to produce a
number of identical copies of the embryo.
 This is done through the method of embryo splitting.
Gene Therapy
 Gene therapy is a technique which may be used to replace a faulty
gene, or to introduce a new gene whose function is to cure or to
favourably modify the clinical course of another gene.
 The vector used to do this is usually a virus.
 There are considerable challenges when developing successful
gene therapy for specific conditions. For example:
 The condition being treated must be well understood.
 The underlying faulty gene must be identified and a working copy of
the gene must be available.
 The specific cells in the body requiring treatment must be identified
and accessible.
 A means of efficiently delivering working copies of the gene to these
cells must be available.
 There are also a number of ethical issues to consider.
Stem Cells: A New Approach
 Stem cells are another way in which we can alter
evolutionary processes.
 Stem cells can be used to replace cells which have
been lost or damaged in some way.
 For example:
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Alzheimer’s disease
Type 1 Diabetes
Parkinson’s Disease
Spinal Cord Injuries
Stem Cells
 Stem cells are cells which can differentiate into any
other cell in the body.
 There are different types of stem cells. For example:
 Embryonic stem cells – these are from early embryos.
 Adult stem cells (somatic stem cells) – obtained from
bone marrow, skin and umbilical cord blood.
Stem Cells
 Embryonic stem cells come from a four to seven-
day-old blastocyst (early embryo). They have the ability
to form virtually any type of cell found in the human
body, but are not capable of developing into a whole
new organism.
 Embryonic germ cells are derived from the part of a
human embryo or fetus that will ultimately produce
eggs or sperm (gametes).This called the gonadal ridge
found at 6 to 9 weeks of gestation when the embryo is
developing into a fetus. Little research is now
performed using this type of cells because they do not
appear to be as versatile as embryonic stem cells.
Stem Cells
 Adult stem cells are more specialised than embryonic
stem cells. They are found in the majority of tissues
and organs in our body and generate the mature cell
types within that tissue or organ. They have a
restricted ability to produce different cell types and to
self-renew.
 Umbilical cord blood stem cells are collected from
umbilical cords at birth. They are capable of producing
all of the blood cell types in the body. Cord blood stem
cells are currently being used to treat patients who
have undergone chemotherapy.
Stem Cells
Stem cells that have the potential to develop into any of
the cell types found in an adult organism are called
pluripotent. Embryonic stem cells and embryonic germ
cells are pluripotent.
Stem cells that only have the potential to make a few cell
types in the body are called multipotent.
Cells that are capable of forming a completely new
embryo that can develop into a new organism are called
totipotent. A fertilised egg is totipotent as it has the
potential to develop into a new organism.
Therapeutic cloning for stem cell
therapy
 Therapeutic cloning refers to cloning for the purpose of
treatment.
 Therapeutic cloning involves the creation of an embryo
through the nuclear transfer technique.
 The cell used in the nuclear transfer is a healthy cell
from the patient, allowing the use of a perfect genetic
match.
Ethical Issues
 The use of stem cells from early embryonic cells has caused
a lot of ethical debate.
 It has been argued that it should be illegal as it is destroying
an embryo which could potentially develop full term.
 There are many laws and acts which researchers are legally
bound by.
 Researchers can only use ‘excess’ embryos.
 They must have written permission by each individual
responsible for the embryo.
 Researchers must have a special license to carry out research
on embryos.
 Embryos cannot be created for research purposes.
Genetic Screening
 Genetic screening involves the analysis of a DNA sample
in order to determine the presence of one or more
alleles associated with inherited disorders.
 There are many reasons why genetic screening may be
carried out:
 an adult may be screened to determine if they carry a
particular allele
 An embryo can be screened to see if they are affected by
any inherited diseases (e.g.: Down Syndrome)
 Pre-natal tests may be carried out to confirm if an unborn
fetus is affected by a genetic disorder.
 Predictive testing may also be carried out in order to
identify the risk of developing a late-onset disease.
Human Reproduction
 There are many ways in which human reproduction can
be altered.
Stopping
Conception
Overcoming Infertility
 There are many different ways in which infertility can
be overcome, in order to allow couples to conceive.
 Some examples are:
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Donor insemination
IVF
Donation of eggs
Surrogacy
Gamete intrafallopian transfer
Intracytoplasmic sperm injection
Donor Insemination
 This involves the fertilisation of the woman by donor
sperm.
 This is used widely by infertile couples where the
problem lies with male being unable to produce viable
sperm.
 It is also widely used by lesbian couples wanting to
conceive.
IVF – In-Vitro Fertilisation
 IVF is used by couples who produce normal viable
gametes, but are unable to conceive for other reasons,
such as damaged fallopian tubes.
 In IVF, eggs are collected from the female, and sperm is
collected from the male, and these gametes are fertilised
external to the females body.
 One, or several of the successful embryos are the
implanted into the female.
 Any excess embryos may be stored in liquid nitrogen for
future use.
Donation of Eggs
 Some females have difficulties producing eggs.
 In this case, an infertile woman may use eggs from
another female.
 The sperm to fertilise the egg is collected from the
woman’s partner.
Surrogacy
 Surrogacy is the process where one female carries the
child of another female, who for some reason or
another cannot carry her own baby.
 This procedure is also used by gay dads wanting to
conceive.
 One of the major issues surrounding surrogacy is the
fact that the woman acting as the incubator can
become attached to the child they’ve been carrying for
9 months.
Gamete Intrafallopian
Transfer
 This is used by couples who can both produce viable
gametes, but for some reason these gametes are
physically prevented from meeting.
 In this technique, the gametes are collected from both
individuals and then introduced into the fallopian tube
of the female. The gametes then have a chance to
fertilise.
Intracytoplasmic Sperm
Injection
 This is a technique used when the male cannot
produce a high enough sperm count to achieve normal
conception.
 An embryologist chooses a single sperm which is more
motile and this is then injected into the egg cell.
 This is then implanted into the female through the IVF
procedure.