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Genetics - part one
Simple Genetics
(One Gene for One Trait)
n  Mendel’s
Pea Plants.
–  Tall or short.
–  Round or wrinkled.
–  Etc…
n  Dominant
& recessive.
or Hybrid.
n  Simple Punnett Squares.
n  Purebred
Gregor Mendel
TEST 1 on SLIDES 1-19
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n  Gregor
Mendel was a
monk who worked with
pea plants in the mid
1800’s. Today he is
known as “Father of
Genetics.”
He was curious about
the “factors” acting
on inheritance.
Are there patterns?
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What is Genetics?
n  Genetics
is the branch of biology that
deals with heredity.
n  Heredity
is the passing of traits from
parents to offspring.
–  Parents à offspring
n  Traits
are characteristics of an organism.
–  Human examples: height, hair, eye color.
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Genetics - part one
n 
Gene: a section/piece of DNA on a chromosome
that codes for a specific trait.
§  Alleles = alternate forms of a gene (Ex: Blood type A/B/O).
§  Genes tend to come in pairs (alleles).
n 
DOMINANT: an allele whose trait always shows
up in the organism when the allele present.
–  (CAPITAL
n 
LETTER)
recessive: an allele hidden by dominant.
–  (lower
case letter)
n 
Genotype: genetic makeup; allele combinations.
n 
Phenotype: physical appearance of an organism
– 
(Ex: BB, Bb, bb)
(Ex: Brown hair)
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How to make a test cross
(aka Punnett Square)
Parent #2 alleles
Parent #1 alleles
Offspring
Offspring
Offspring
Offspring
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Genetics - part one
Diagrams & math can be
used to predict the
probability that a trait will
pass from parent(s) to
offspring.
Punnet Squares
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Complete this test cross between two purebred pea plants:
T
T
t
t
T = tall stem
t = short stem
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Genetics - part one
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Where are genes?
n 
Genes & chromosomes come in pairs. Most
human cells have 23 pairs of chromosomes in
the nucleus containing just under 30,000 genes.
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Genetics - part one
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CHROMOSOMES
n 
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Half from each gamete (sperm and egg).
But what about asexual reproduction???
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Code Conservation
n 
All species on
Earth use the
same chemical
code (GTCA).
Biodiversity
comes from
SNP’s along a
gene sequence.
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Genetics - part one
Must Know
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Allele
Chromosome
DNA (GTCA)
Dominant
Gene & Genetics
Genotype
Heterozygous
Heredity
Homozygous
Hybrid
Meiosis
Mutation
Offspring
Phenotype
Probability
Punnett Square (Cross)
Purebred
Recessive
Traits
Challenge
Terms
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Central Dogma
Co-dominance
Dihybrid cross
Diploid
Haploid
Histones
Gametes
Locus (Loci)
Mutagen
Pedigree chart
Purines (A & G)
Pyrimidines (T & C)
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Challenge
Mendel’s Dihybrid cross
n  We
can look at two traits simultaneously
using a dihybrid cross.
n  Consider shape & color in peas
–  R: round r: wrinkled
–  Y: yellow y: green
–  Cross two heterozygotes RrYy x RrYy
–  Try in your notes now!
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RY
Ry
ry
rY
RY
Ry
ry
rY
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Genetics - part one
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GENETICS PART
TWO
-COMPLEXNON-MENDELIAN
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DNA Structure understood
1953
Watson & Crick
Rosalind Franklin
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Genetics - part one
DNA
*Human Genome mapped in 2003
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Central Dogma
DNA à mRNA à Protein
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The Limits of Mendel’s work
n 
Mendel’s experiments with pea plants looked at
one gene for one trait.
–  This pattern of inheritance is called Mendelian..
§  Some examples: Cheek dimples, face freckles & cleft chins
§  Tom Bradyà
n 
Few human traits actually obey this model
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Genetics - part one
Polygenic Traits
n 
Most human traits are polygenic, which means
they are controlled by multiple genes.
–  This leads to a wide array of phenotypes.
–  Simple Punnett squares do NOT work for
polygenic traits.
§  EX: Human height & eye color.
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Dynamic Development (GxE)
n 
Genes interact with their environment (GxE)
–  In other words, there is a relationship
between your genetics & the way you live
your life.
§ Nutrition, hormones, sensory input,
physical and, etc…
n  Epigenetics:
Markers & tags (i.e. methyl
along with histones affect the
epigenome of an organism.
groups),
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Mutations
n  Mutations
are changes in the DNA bases.
–  G. T. C. A.
–  Change can be letter addition,
substitution, deletion or inversion.
n  Mutations
can be good, bad or indifferent
to an organism.
n  Mutagens are agents capable of causing a
mutation, such as UV light or certain chemicals.
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Genetics - part one
Mutations & Evolution
n  Mutations
drive evolution.
–  Since all living things use the same chemicals
(G.T.C.A.) for their “code,” changes are
necessary to give rise to new species.
§  A concept better known as genetic variation.
–  Observed at the taxonomic levels (D.K.P.C.O.F.G.s.)
n  Genetic
Variation à Biodiversity.
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Glowing mutant mice, frog/duck genetic
mutants.
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Drug resistant bacteria, mushroom
mutant, lungfish, tomato mutations.
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Genetics - part one
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Quotes:
n  “It’s not that I’m so smart, it’s just that I stay with
problems longer.” -Albert Einstein.
n 
“I'm not out there sweating for three hours every day
just to find out what it feels like to sweat.” -Michael
Jordan.
n 
“Some people want it to happen, some wish it would
happen, and others make it happen.” -Michael Jordan.
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CALGENE 1994-1997
First GM Tomato approved by FDA
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Genetics - part one
Human Genome Project
1987-2003.
[~3.3 billion base pairs]
Faroe Islands (Denmark)
~ 50,000 People. Genome sequencing
project for entire population (2013)
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