Applications of Genetics - My Class Sites

tanktherapistBiotechnology

Oct 23, 2013 (3 years and 11 months ago)

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SBI3U

Mr. Tabone

Manipulating Genes


Even before Mendel humans have been using
selective breeding
to manipulate plant and animal
populations



Domesticating dogs, increasing milk or wool
production from livestock, using seeds from a hardy
crop





Selective Breeding


Benefits


Desirable traits can be kept and undesirable trait
can be eliminated from future generations



Drawbacks


Low genetic variety


Susceptibility to disease


High chance for expression of harmful recessive
alleles (
eg
. albinism)

Hybridization


When 2 different species are bred together to create a
new species


The new species is sometimes fertile and sometimes
sterile


Eg
: Loganberries are fertile hybrids of blackberries
and raspberries


Eg
: Seedless watermelons are sterile hybrids



Done to create crops resistant to weather conditions or
disease, or to have desirable characteristics (no seeds)

Cloning


Cloning is a term that refers to creating an exact copy of
an organism from one single cell


This is exactly what happens in mitosis



The biotechnology technique is slightly different from
normal mitosis however



Multicellular organisms have two classes of cells


Stem cells and Specialized cells


Specialized cells have specific functions and are quite
different from one another (muscle vs. brain vs. skin etc.)


Stem cells can divide and create any type of specialized cell




Cloning


Since specialized cells do not normally divide to create
different specialized cells


Muscle cells only divide into muscle cells, they do not create
brain cells (for example)



Adults are mostly composed of specialized cells, with very
few stem cells


Therefore creating a clone animal out of a specialized cell is
difficult



Traditionally stem cells have been used for the purpose of
cloning

Cloning


Recently there have been many breakthroughs in this
area, and some specialized cells can now be turned into
clone cells and used for cloning



This is still a very active area of research




Dolly the sheep


Many species of animals have been successfully cloned


All have had short life spans and exhibited many
physiological problems, like arthritis, premature aging,
and lung disease


Click and Clone

Applications of Cloning


We can genetically modify certain organisms to give
them advantageous traits and then clone them to
produce several identical organisms


Eg
: Producing corn plants that can grow in cold weather,
or cows that produce more milk than normal


Cloning allows us to produce several organisms with our
specific modifications



We already do this for several of our fruits and
vegetables



Homework pg 151 #1
-
9, 11, 12


Gene Therapy


Using genes to treat disease



Used in two different ways


A normal gene product can be given to affected
individuals



Manipulate genes in parents or offspring to treat
the disease


Gene Therapy


Using gene products to treat disease


Leptin and obesity



Obese mice lack the receptor for the


protein leptin


Leptin controls appetite



Leptin injections can help control obesity




Gene Manipulation


Involves replacing defective genes with properly
functioning ones


Eg
: replacing the non
-
functional gene that codes for
leptin receptors in obese mice with a properly
functioning one



Will often use specially
-
tailored viruses to deliver
genes



Difficult to get copies of the desired gene into enough
cells in the target tissues

Gene Manipulation


Problems with immune response to the viruses



Problems with division in the new cell line



Some success has been seen with adenosine
deaminase

deficiency (ADA)


Defect in a key protein involved in the immune
response


Bone marrow stem cells are removed, manipulated,
and replaced


Mutation


How are different alleles created?


One way is by mutations



Mutations are changes in the DNA sequence



Since DNA codes from protein synthesis, changing the
DNA can alter the proteins made or stop them from
being made all together



This can be both useful and detrimental

Mutations


Mutations can be caused
several different ways,
including;


Substitution


One base pair change


Deletion


Removing a section of DNA


Insertion


Inserting a section of DNA

Mutagens


Anything that alters DNA is labelled
as a mutagen


Radiation and several chemicals
can act as mutagens



Mutations in somatic cells often go
unnoticed


Mutations in gamete cells are passed
on



Cancer can be caused by mutation

Sickle Cell Anemia


A blood disorder caused by a recessive


mutation on an autosomal chromosome



Blood cells are shaped like crescents


instead of their normal shape




Sickle cells are not efficient at carrying oxygen



Being heterozygous for sickle cell anaemia confers
resistance to malaria

Genetic Screening


Geneticists can identify if a person has an increased
risk of inheriting a disorder


Genes can give an increased susceptibility to certain
diseases



Huntington Disease


Autosomal dominant


Onset after 30
-
40 years of age


Diminished mental capacity and uncoordinated
muscle movements


Genetic Screening


Cystic fibrosis


Large amount of mucus lining the lungs and
digestive tract


Autosomal recessive trait



Would you want to know if you were susceptible to a
certain disease?



Or if your kids would be susceptible?

Genetic Counselling


Counsellors determine whether an individual is at risk
of inheriting detrimental traits


Such as sickle cell anemia, or a predisposition for
cancer



It is possible that in the future we can know all the
susceptibilities and predispositions an individual will
have



What implications does this have for society?

Prenatal Diagnosis


Testing a fetus for problems before birth



Process is called amniocentesis


Extracting amniotic fluid (which contains some
cells) with a syringe


Guided by ultrasound



Allows parents to be


prepared for any special


needs before birth