In 2004 Finian Maynard of the British Virgin Islands reset the sailing speed record at 47 knots or 5

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In 2004 Finian Maynard of the British Virgin
Islands re-set the sailing speed record at 47
knots or 54 mph on a windsurfer. He and others
are going for 50 knots.
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Applications and Interviews - SOON
Attend an information open house Feb 8 (Thur
sday) or Feb 13 (Tuesday) 408 Natural History Bu
ilding 7-9 pm Sign up for an interview App
lications at the info sessions
email ibhonors (_at_life.uiuc.edu) for more inform
ation
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BIOLOGY RESEARCH SYMPOSIUM
Illini Biological Societys

• Interested in working in a campus research lab?
• Come learn about the benefits and available
  undergraduate and graduate research opportunities
  at UIUC!

February 7th, 7PM, 217 Noyes
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Lecture 9 Genetics Complex inherited patterns
variation
Readings Ch. 14, 14.3 to end
You need to be able to explain the following to
yourself and to me (on exams)
Complex patterns of inheritance not described by
Mendel Partial dominance dominance depends on a
nalysis Tay-Sacks disease Multiple alleles ABO
blood group locus  Epistasis an allele of one
gene can mask an allele of another gene
epistasis in mouse coat color, and in other
cases
Pleiotropy a single allele may have multiple
effects on phenotype. sickle cell allele Polyg
enic inheritance
Environmental effects
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Post-Mendelian studies have revealed that
relationships between genotype and phenotype can
be complex

• degrees of dominance
• multiple alleles
• epistasis
• pleiotropy
• polygenic inheritance
• environmental effects

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Partial dominance basic idea level of analysis
Tay-Sacks disease
Snapdragons
www.florifacts.umn.edu/Trials/Annual20Beddin...
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Partial dominance basic idea level of analysis
Tay-Sacks disease
Example of incomplete dominance
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Partial dominance basic idea level of analysis
Tay-Sacks disease
Assessment of dominance depends on the level of
analysis!
A heterozygote may display a dominant phenotype
at the organismal level, but at a biochemical
level may show incomplete dominance.
Tay-Sachs disease caused by absence of an
enzyme, hexosaminidase A (Hex-A)
Homozygous dominant normal levels of Hex-A,
normal development of child Homozygous recessive
no Hex-A, death of child by age 5
Heterozygote1/2 normal levels of Hex-A, normal
development of child
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Assessment of dominance depends on the level of
analysis!
Survival
short life
long life
Complete Dominance
HexA/ HexA
HexA/ HexA-
HexA-/ HexA-
Tay-Sachs
Amount of hexaminidase
none
lots
Incomplete Dominance
HexA-/ HexA-
HexA/ HexA
HexA/ HexA-
Tay-Sachs
HexA- codes for a nonfunctional enzyme.
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Codominance in platyfish, Xiphophorus maculatus
dominance relationships partial, incomplete cod
ominance
Ray, RR
Ray Spot, RS
Spot, SS
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A medical problem - some blood transfusions
produce lethal clumping of cells.
Dont worry about details yet...
Multiple alleles ABO blood groups
Type A blood transfused into Type B person
Type B blood transfused into Type B person - OK
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Multiple alleles ABO blood groups
Table 14.2
There are 3 different alleles, IA, IB, and i
Allele IA makes a cell surface antigen,
symbolized with a triangle IB makes a different
antigen, symbolized as a circle
i makes no antigen
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Multiple alleles ABO blood groups
Human ABO Blood Groups
Gene I specifies which sugar is found on the
outside of red blood cells 3 alleles are presen
t in the human population IA N-acetyl-galactos
amine IB galactose i (also referred to as o)
no sugar present 6 possible genotypes
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Multiple alleles ABO blood groups
Immunology 101 Sugar on the blood cell is an an
tigen (A, B, A and B, or none)
Your immune system thinks your own antigens are
fine Your immune system makes antibodies against
non-self antigens Antibodies recognize and targ
et cells with antigens for destruction
something that elicits an immune response
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Multiple alleles ABO blood groups
The Human ABO Blood Group System
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Multiple alleles ABO blood groups
The Human ABO Blood Group System
multiple alleles
codominance
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Multiple alleles ABO blood groups
Codominance in the ABO Blood Group System
Dominance
Dominance
Codominance
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Epistasis non-epistasis mouse coat color explan
ation
A 9331 ratio is the standard result for a
dihybrid cross
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Epistasis non-epistasis mouse coat color explan
ation
Epistasis Normal dihybrid ratio is altered from 9
331 to
9340
C/c gene is epistatic to the B/b gene
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Color genetics in Cape Primrose (Streptanthus) -
an explanation for how epistatis works.
Epistasis non-epistasis mouse coat color explan
ation
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Color genetics in Cape Primrose - an explanation
for how epistatis works.
Enzyme 1
Enzyme 2
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Color genetics in Cape Primrose - an explanation
for how epistatis works.
Genotype F functions f does not
Enzyme 1
F/F or F/f
Enzyme 2
Could be mauve or blue, but not rose
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Color genetics in Cape Primrose - an explanation
for how epistatis works.
Genotype F functions f does not
X
f/f
Enzyme 1
Enzyme 2
Will be rose regardless of genotype at gene D -
gene O is epistatic to gene D
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Pleiotropy one gene causes multiple effects on
phenotype
Pleiotropy sickle cell disease
Sickle cell anemia one mutant gene, many symptoms
Single amino acid substitution in the hemoglobin
protein
Pain, stroke, leg ulcers, bone damage, jaundice,
gallstones, lung damage, kidney damage, eye damag
e, anemia, delayed
growth
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Polygenic inheritance additive effects
(essentially, incomplete dominance) of multiple
genes on a single trait
Polygeny
AA dark Aa less dark aa - light And similar
ly for the other two genes - in all cases
dominance is incomplete for each gene.
Think of each capital allele (A, B, C) as
adding a dose of brown paint to white paint.
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Environmental effects

• environment often influences phenotype
• the norm of reaction phenotypic range due to
  environmental effects
  
• norms of reactions are often broadest for
  polygenic characters.

Blue require low pH acidic soils
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Environmental effects
Environmental effects effect of temperature
on pigment expression in Siamese cats
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Lecture 9 Genetics Complex inherited patterns
variation
Readings Ch. 14, 14.3 to end
You need to be able to explain the following to
yourself and to me (on exams)
Complex patterns of inheritance not described by
Mendel More on partial dominance dominance depe
nds on analysis Tay-Sacks disease
Multiple alleles ABO blood group locus  Epistas
is an allele of one gene can mask an allele of
another gene epistasis in mouse coat color, and
in other cases
Pleiotropy a single allele may have multiple
effects on phenotype. sickle cell allele Polyg
enic inheritance
Environmental effects