4.3: Reproductive Strategies and Technologies
pg. 182
Reproductive Strategies in Agriculture
Selective breeding: the process of breeding plants and animals for
desirable traits.
Artificial insemination: the process by which sperm are collected
and concentrated before being introduced into the female’s
reproductive system.
Embryo transfer: the process by which an egg that has been
fertilized artificially is transferred into a recipient female’s uterus.
Reproductive Technologies for Human
Assisted Reproductive Technologies (ART), such as; artificial
insemination is used in humans to help adults who are unable to
conceive a child.
The sperm is collected from a donor, (male partner), and
introduced into the women’s vagina.
In vitro fertilization: the technique used to fertilize egg cells
outside the female’s body.
Figure 4.24: After the sperm and egg are put together in laboratory glassware, they are
incubated together for about 18 hours to allow fertilization.
Pre-implantation Genetic Diagnosis
Parents who have a history of genetic disorders in their family may
choose to use a process that allows for the diagnosis of genetic
disorders soon after fertilization.
The testing is done before the embryo is implanted. It can be
diagnosed, called Pre-implantation Genetic Diagnosis, (PGD).
After in vitro fertilization, the zygote is allowed to divide over two
days, than a cell is removed to be analyzed.
Further developments in IVF, have improved the success rates for
human reproduction, these advancement have led to ethical and
social debates, such as; abuse of the technology.
Cloning: Reproduction of Exact Copies
Cloning: is a process which produces identical copies of a gene,
cell, or an organism.
Gene Cloning: is the use of DNA manipulation techniques to
produce multiple copies of a single gene or segment of DNA.
Recombinant DNA: a molecule of DNA that includes genetic
material from different sources.
1. Isolate the segment of DNA to clone, and choose a vector for cloning. Vectors
act as carriers of the DNA to be cloned so that the DNA can be copied in a
foreign cell. One commonly used vector for cloning in bacteria is called a
plasmid. Plasmids are small, circular pieces of DNA that remain distinct from
the bacterial chromosomes.
2. Insert the chromosomal DNA into the vector. This relies on the use of
reagents that can cut DNA and help different pieces to join together. The
resulting DNA molecule, which includes genetic material from different
sources, is called recombinant DNA.
3. Treat foreign cells, such as: bacterial cells, so that they take in the
recombinant DNA. The process of taking up the recombinant DNA is called
transformation. Once the recombinant DNA plasmid is taken into the cell,
many copies of the cloned gene or DNA fragment will be made by the host
cell.
Figure 4.25: A gene or piece of DNA can be cloned. Many copies of it or the protein
product that the gene codes for can be produced and isolated.
Learning Check, questions 19 – 24, pg. 185.
Therapeutic Cloning and Reproductive Cloning
Therapeutic Cloning: the process of replacing an egg cell’s
nucleus with the nucleus from a somatic donor cell to produce a
cell line of genetically identical cells
Reproductive Cloning: the process of producing genetically
identical organisms.
Figure 4.26: Therapeutic and reproductive cloning involves inserting the nucleus from a
somatic cell of the doctor into an egg cell that has had its nucleus removed.
Therapeutic Cloning and Stem Cells
Stem Cell: an undifferentiated cell that can develop and become
specialized into different cell types of the body.
Three different sources for stem cells:
- Embryonic stem cells, which are obtained from embryos.
- Adult stem cells, which are somatic cells that have retained the
ability to differentiate into some other cell types.
- Induced pluripotent stem cells, which are specialized adult stem
cells that have been induced to return to a stem-cell-like state.
Figure 4.27: Stem cells can be stimulated to differentiate into specific tissue types under
the right conditions. Potential applications for stem cells include treating diseases and in
regenerative medicine.
Transgenic Organisms
The technique of inserting foreign DNA into plants and animals
produces transgenic organisms.
Transgenic organisms: are organisms whose genetic material
includes DNA from different species.
Genetically modified organism or GMO, is an organism which
have their genome altered for a specific purpose.
These modifications can increase their resistance to herbicides,
insect pests, or viruses.
These modified organisms can have their nutrient value increased
to support populations lacking in some nutrients such as: iron and
vitamin A.
Transgenic plants can also be used for medical purposes, such as:
producing insulin in sunflower plants.
Figure 4.28: This transgenic product, golden rice, contains four different foreign genes.
Three of these genes come from other plants, and one comes from a fungus.
Applications of Transgenic Animals
Transgenic animals can be used in laboratory experiments to study
diseases and ways to treat them. Other animals, goats can produce
medical protein in their milk, such as: human growth hormone
and anti-clotting factors.
Other transgenic animals can ac as human organ donors, such as;
pigs with genetically modified tissue that is compatible to human
tissue and is not rejected. Is it really ethical to create animals for
the soul purpose of harvesting organs?
Regulating the Use of Transgenic Organisms
Environmental Threats: herbicide resistant plants may require
stronger herbicides if genes may cross into other plants, creating
super plants.
Health Effects: Long term effects are unknown, consuming food
and medicine may have negative effects.
Social and Economic Issues: Benefits to human health and reduce
hunger, but the amount of money spent may be greater then
benefits.
Figure 4.29: Genetic engineering can create transgenic animals that secrete human
proteins or other substances in their milk.
Section 4.3 Review: questions 1 – 16, pg. 190