Transcript Genetic Transfer PPT

Genetic Selection and Transfer
Compiled by: IMS
Stolen and edited by: Brandon Freel
Objectives
 Investigate genetic selection
methods.
 Develop a logical argument for
cloning.
 Distinguish between embryonic
cloning and nuclear transfer.
Genetic Selection
•Permanent improvements in domestic
animals can be made by genetic
selection through natural or artificial
means.
•Natural selection occurs in wild
animals, while artificial selection is
planned and controlled by humans.
Genetic Selection
•Animals that exhibit desirable traits
are selected and mated.
•Animals that exhibit undesirable
traits are not allowed to reproduce or
are culled from the herd.
Photo by Peggy Greb courtesy of USDA Agricultural Research Service.
Genetic Selection
•The goal of selection is to increase the
number of animals with optimal levels of
performance, while culling individuals with
poorer performance.
•Genetic improvement is a slow process and
can take several generations to see an
improvement in a trait.
Genetic Selection
Artificial insemination and embryo
transfer are breeding methods that are
commonly used to decrease the time
taken to improve a trait.
“Angus surrogate mother nurses her
Romosinuano embryo transfer calf.
Initially, scientists are investigating
the influence of surrogate breed on
Romosinuano calf traits such as
length of gestation and birth and
weaning weights” (USDA-ARS)
Photo by Scott Bauer courtesy of USDA Agricultural Research Service.
Genetic Selection
•Traits are passed from parents to
offspring, but some traits are more
heritable than other traits.
•That is, the genotype of an individual
will be expressed more strongly and
environment will be less influential for
particular traits.
Heritability of Various Traits in Livestock
Trait
Sheep Swine Cattle
Weaning weight
15-25% 15-20% 15-27%
Post-weaning gain
efficiency
20-30% 20-30% 40-50%
Post-weaning rate of gain 50-60% 25-30% 50-55%
Feed efficiency
50%
12%
44%
Loin eye area
53%
53%
56%
Genetic Selection
•Several genes
influence some traits.
•For example, rate of
growth is a trait that is
influenced by appetite,
energy expenditure,
feed efficiency, and
body composition.
Genetic Selection
•Breeding systems aim to improve a
single trait or multiple traits.
•Single trait selection – aimed at
improving one trait in a breeding
program with little or no regard for
improvement in other (associated) traits.
Genetic Selection
•Multiple trait selection – aims to
simultaneously improve a number of
traits.
•Theoretically, multiple trait
selection should result in a faster
rate of gain toward a specific
objective.
Genetic Selection
•Most domestic species now have a
recognized system in place that allows
breeders to estimate the genetic merit of
individuals.
•In the United States, cattle, sheep,
goat, and swine breeders use expected
progeny differences (EPDs).
Genetic Selection
EPDs are used to compare animals from
the same species and breed.
“Newly developed EPDs (expected
progeny differences) make it possible to
select for tenderness and carcass and
beef quality traits in Brahman cattle,
shown here at the ARS Subtropical
Agricultural Research Station in
Brooksville, Florida” (USDA-ARS).
Photo by David Riley courtesy of USDA Agricultural Research Service.
Genetic Selection
For EPD values to be used effectively,
one needs to know the breed averages,
the accuracy of the EPDs, and who
estimated the EPDs.
A high EPD is not necessarily good; it
depends on the trait being considered
and breeding objectives.
Modern Genetics
•In recent years, traditional methods of
improvement through selection and breeding
have been superceded by genetic
manipulation.
•A substantial amount of research has
focused on direct manipulation of genes and
DNA.
Gene Transfer
Genetic engineering basically
refers to transferring a gene
from one individual to another.
Gene Transfer
•Scientists are able to code genes for
desirable compounds and insert them
into other cells, such as
microorganisms.
•These microorganisms produce these
desirable compounds on a large scale.
Gene Transfer
This area of genetic manipulation
makes important contributions to
domesticated animals in relation to
immunology, vaccines, aging, and
cancer.
Photo by Scott Bauer courtesy of USDA Agricultural Research Service.
Gene Transfer
The implications for introducing
superior production, conformation,
and disease-resistant traits into
domestic animals through gene
transfer hold considerable promise
in the genetic improvement of
animals.
Cloning
Embryonic cloning of animals involves
the chemical or surgical splitting of
developing embryos shortly after
fertilization and, consequently,
developing two identical individuals.
Cloning
The separated embryos are
allowed to culture, or grow, to a
more advanced embryonic stage
before they are implanted into the
uterus of a recipient mother for full
development.
Nuclear Transfer
Nuclear transfer is another method
of cloning that involves the
microsurgical collection of nuclear
material from a donor cell which is
then transferred into an unfertilized
ovum that has had its own nucleus
removed.
Nuclear Transfer
The cells that develop
successfully become
identical individuals.
Dolly the Sheep (the first
mammal cloned from adult
cells) and many other
species have been cloned
this way.
Photo courtesy of Wikipedia.
Nuclear Transfer
Worldwide, the institute that has
cloned the most species is Texas
A&M University, College of
Veterinary Medicine, which to date
has cloned cattle, swine, a goat, a
horse, deer, and a cat.
Nuclear Fusion
Another innovation in genetic
engineering, called nuclear
fusion, involves the union of
nuclei from two gametes,
male or female sex cells.
Nuclear Transfer
This fusion shows promise for
the uniting of nuclei from two
outstanding females, two
outstanding males, or the
normal outstanding male and
female combination.
Nuclear Transfer
The possibility for selecting
desired traits at the cellular
level holds exciting implications
for the genetic improvement of
domestic animals.
Objectives
 Investigate genetic selection
methods.
 Develop a logical argument for
cloning.
 Distinguish between embryonic
cloning and nuclear transfer.