Genetics

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Genetics
Def the study of reproduction and the results
of the combination of chromosomes.
Gregor Mendel (1822 1884)
Austrian Monk who is considered Father of
Genetics
Mendels Laws
1. Law of Segregation
- Chromosomes separate (segregate) into
different gametes during meiosis.
2. Law of Independent Assortment
All Chromosomes segregate independent of each
other. None are connected to each other
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Example of Independent Assortment
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Mendel talked about traits and called the genes
for those traits alleles.
Allele -
the different genes for a trait
The traits that you got
when sperm and egg
came together was
NOTHING but probability.
A roll of the dice or a flip of a coin
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Mendel also gave us the genetics terms Dominant
and Recessive
A trait that will ALWAYS show up if it is
in the genes
Dominant -
Recessive -
A trait that will ONLY show up if there are no
dominant genes present
Example Your Mom gives you the gene for having
a Unibrow (recessive) and your father
gives you the gene for having two eye brows
(dominant)
What are you?
Mom
Dad
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Lets look at some traits
DOMINANT Black color
This dogs genetics could be two ways
We show it like this
B from one parent, B from the other parent
OR
B from one parent, b from the other parent
BB is Homozygous for the trait.
Bb is Heterozygous for the trait.
Recessive lighter color
This dogs genetics CAN ONLY be shown one way
b from one parent, b from the other parent
Recessive traits are ALWAYS homozygous thus it
would be bb
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OK, now for a problem
If I have a heterozygous black male and a golden
that
X
mate, what are the chances of having golden
puppies in a litter?
b b
B b
50 black 50 golden
100 golden
You either multiply it out or make a Punnett
square
Or
b
b
50 X 100 50
Bb
Bb
50
B
bb
bb
b
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Definitions to know
Genotype what the genes say
(heterozygous or homozygous).
Phenotype physical appearance of the
organism (black or golden).
P Generation the parents in the problem
F1 Generation the first filial child, first
generation after the parents.
F2 Generation the second generation after
the parents.
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Genetic Practice Problems
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Breed the P1 generation

• tall (TT) x dwarf (tt) pea plants

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Solution
tall (TT) vs. dwarf (tt) pea plants
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Breed the F1 generation

• tall (Tt) vs. tall (Tt) pea plants

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Solution
tall (Tt) x tall (Tt) pea plants
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Everything is not always clear cut
Incomplete Dominance
One allele can not completely dominate the other.
Codominance
When both dominant alleles show in the offspring.
Red
White
Roan offspring
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Multiple Allele Traits
Example
Traits having more than one allele that can be
found in the population.
Human Blood Types
Type A, Type B, Type AB, Type O
Four distinctly different types
Polygenic Traits
Example
Human hair color
Traits that are controlled by several genes at
the same time.
Black, Brown Blonde Red
Four major colors blended through more than a
dozen different allele groups.
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So what can go wrong?
During Meiosis, sometimes the chromosomes do not
split into the different sex cells.
Non Disjunction
when chromosomes do not
split in anaphase1 of Meiosis.
Tri-somy
having three of any given chromosome.
X
The offspring now has three of one of the pairs
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Mono-somy
having only one chromosome for a pair of
chromosome.
Tri-somy Examples
Tri-somy 23 (sex determination)
X X Y - Kleinfelters Syndrome
X Y Y - Superman Syndrome
Tri-somy 21 Down Syndrome
Mono-somy Example
Mono-somy 23 (sex determination)
Turners Syndrome - single X
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Genetic Engineering
Definition
manipulating the genes of an organism due to
selective breeding or microbiological processes
Selective Breeding
selecting certain individuals to be the parents
of the future generations.
All of these things are products of selective
breeding
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Hybridization
Crossing two wild species to try to get a
hybrid with the best traits of the parent
species.
Hybrid Vigor
Having an offspring species that is better in
many ways than either of the parent species
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Genetic Manipulation
Recombinant DNA
The process of manipulating a gene by taking
genes from one organism and moving them to
another.
Step 1 Isolation of target gene.
Lets say that there is a gene in this corn that
is drought resistant.
enzymes
Researchers use enzymes to isolate and cut the
gene out (excise) from the original corn.
Target Gene
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Step 2 - Copy the gene
Using a machine called a PCR (polymerase chain
reaction), the geneticist make thousands of
copies of the gene
Step 3 Insertion of gene
Using enzymes again, the geneticist inserts the
gene into the genetic code of the target plant.
Step 4 Testing of results
Field Biologists set out plots to test the
drought resistance of the new plants.
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Organisms that have the genes of other organisms
are called Transgenic organisms
Examples
Transgenic Yeast cells
Produces human insulin
Drought-resistant Barley
Can live in little water and some in salty water
environments
Herbicide resistant and Pest Resistant Corn
Plants that will not die when weeds around them
are sprayed, and some species that pests do not
want to eat
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Cloning
Target sheep
Donor sheep
nucleus
Process
Take a cell from your organism and an egg from a
donor female.
Take the nucleus from the donor egg.
Fuse the two cells by electro-shock.
Introduce the right hormones to begin division
becoming an embryo.
Implant the embryo into the donor female.
Embryo
The cloned organism is born.
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Review for Genetics Test
Define

• Genetics 2. Gregor Mendel 3. Allele
• 4. Dominant 5. Recessive 6. Homozygous pairs
• 7. Heterozygous pairs 8. Genotype 9. Phenotype
• 10. P Generation 11. F2 Generation 12. F1
  Generation
• 13. Incomplete Dominance 14. Co-dominance
• 15. Multiple Allele Trait 16. Polygenic Trait 17.
  Non-disjunction
• 18 Polysomy 19. Monosomy 20 Genetic engineering
• 21. Hybridization 22. Hybrid Vigor 23.
  recombinant DNA
• 24. Cloning

Questions

1. What are the two laws that are attributed to
   Mendel?
2. How do they affect genetics?