Download Non-Medelian Genetics

Non-Mendelian Genetics
Mendelian Genetics:
Dominant & Recessive Review
One allele is DOMINANT over the other
(because the dominant allele can “mask” the
recessive allele)
genotype: PP
genotype: pp genotype: Pp
phenotype: purplephenotype: white phenotype: purple
Review Problem:
Dominant & Recessive
In pea plants, purple flowers (P) are dominant over
white flowers (p). Show the cross between two
heterozygous plants.
GENOTYPES:
- PP (25%)
Pp (50%)
pp (25%)
- ratio 1:2:1
PHENOTYPES:
- purple (75%)
white (25%)
- ratio 3:1
P
p
P
PP
Pp
p
Pp
pp
Non-Mendelian Genetics
Incomplete Dominance
Codominance
Multiple Alleles
Polygenic Traits
Sex-Linked Traits
Fur colors
black
agouti
yellow
Incomplete Dominance
 a third (new) phenotype
appears in the heterozygous
condition as a BLEND of the
dominant and recessive
phenotypes.
 Ex - Red (RR) + White (WW) = Hybrid Pink (RW)
RR = red
WW = white
RW = pink
Problem:
Incomplete Dominance
Show the cross between a pink and a white flower.
GENOTYPES:
- RR (0%)
RW (50%)
WW (50%)
- ratio 1:1
R
W
W
RW
WW
W
RW
WW
PHENOTYPES:
- pink (50%); white (50%)
- ratio 1:1
Codominance
in the heterozygous condition, both alleles are expressed
equally with NO blending! Represented by using two
DIFFERENT capital letters.
Example:
Sickle Cell Anemia -
NN =
normal cells
SS = sickle cells NS = some of
each
Codominance Example:
Speckled Chickens
BB = black feathers
WW = white feathers
BW = black & white speckled feathers
Notice –
NO GRAY!
NO BLEND!
Each feather is
either black or white
Codominance Example:
Rhodedendron
R = allele for red flowers
W = allele for white flowers
Cross a homozygous red
flower with a homozygous
white flower.
Codominance Example:
Roan cattle
cattle can be
red
(RR – all red hairs)
white
(WW – all white hairs)
roan
(RW – red and white hairs together)
Codominance Example:
Appaloosa horses
Gray horses (GG) are codominant to white horses
(WW). The heterozygous horse (GW) is an Appaloosa
(a white horse with gray spots).
Cross a white horse with an appaloosa horse.
W
W
G
GW
GW
W
WW
WW
Problem:
Codominance
Show the cross between an individual with
sickle-cell anemia and another who is a carrier
but not sick.
N
S
GENOTYPES:
- NS (50%)
SS (50%)
- ratio 1:1
S
NS
SS
PHENOTYPES:
- carrier (50%)
sick (50%)
- ratio 1:1
S
NS
SS
MULTIPLE ALLELES
• Many traits have more than 2 alleles that
determine the phenotype
Forensic Science
T. Trimpe 2006 http://sciencespot.net/
What is blood made up of?
•
The red blood cells contain
hemoglobin, a protein that
binds oxygen. Red blood cells
transport oxygen to, and
remove carbon dioxide from,
the body tissues.
The white blood cells fight
infection.
The platelets help the blood to
clot, if you get a wound for
example.
The plasma contains salts and
various kinds of proteins.
Blood Facts
The average adult has about FIVE liters of blood inside of
their body, which makes up 7-8% of their body weight.
Blood is living tissue that carries oxygen and nutrients to
all parts of the body, and carries carbon dioxide and other
waste products back to the lungs, kidneys and liver for
disposal. It also fights against infection and helps heal
wounds, so we can stay healthy.
There are about one billion red blood cells in two to three
drops of blood. For every 600 red blood cells, there are
about 40 platelets and one white cell.
http://www.bloodbankofalaska.org/about_blood/index.html
History of Blood Groups and Blood Transfusions
•Experiments with blood transfusions
have been carried out for hundreds of
years. Many patients have died and it was
not until 1901, when the Austrian Karl
Landsteiner discovered human blood
groups, that blood transfusions became
safer.
He found that mixing blood from two
individuals can lead to blood clumping.
The clumped RBCs can crack and cause
toxic reactions. This can be fatal.
•
http://nobelprize.org/medicine/educational/landsteiner/readmore.html
Multiple Alleles
there are more than two alleles for a gene.
Ex – blood type consists of two dominant and
one recessive allele options. Allele A and B are
dominant over Allele O (i)
Blood Types
Type A
Type B
Type O
Type AB
AUTOSOMAL CHROMOSOME
A
The alleles for Blood
group are in the same
place on the
chromosome 9. However
the genes have a
different code giving the
different blood group
B
Susan
one alleles from Pete and one from
Susan.
Pete
AB0 blood grouping system
Blood group A
If you belong to the blood
group A, you have A
antigens on the surface of
your RBCs and B
antibodies in your blood
plasma.
Blood group B
If you belong to the blood
group B, you have B
antigens on the surface of
your RBCs and A
antibodies in your blood
plasma.
Blood group AB
If you belong to the blood group
AB, you have both A and B
antigens on the surface of your
RBCs and no A or B antibodies
at all in your blood plasma.
Blood group O
If you belong to the blood group O
(null), you have neither A or B
antigens on the surface of your RBCs
but you have both A and B antibodies
in your blood plasma.
Multiple Alleles:
Blood Types (A, B, AB, O)
Rules for Blood Types:
A and B are co-dominant (Both show)
IAIA = type A
IBIB = type B
IAIB = type AB
A and B are dominant over O (Regular dom/rec)
IAi = type A
IBi = type B
ii = type O
Allele
Can
Can
(antigen) Donate Receive
Possible
on RBC Blood
Blood
Phenotype Genotype(s) surface
To
From
A
IAi
IAIA
A
A, AB
A, O
B
IBi
IBIB
B
B, AB
B, O
AB
AB
A, B,
AB, O
O
A, B,
AB, O
O
AB
O
IAIB
ii
Problem:
Multiple Alleles
Show the cross between a mother who has type
O blood and a father who has type AB blood.
GENOTYPES:
- Ai (50%)
Bi (50%)
- ratio 1:1
PHENOTYPES:
- type A (50%)
type B (50%)
- ratio 1:1
i
i
A
Ai
Ai
B
Bi
Bi
Problem:
Multiple Alleles
Show the cross between a mother who is heterozygous for
type B blood and a father who is heterozygous for type A
blood.
GENOTYPES:
-AB (25%); Bi (25%);
Ai (25%); ii (25%)
- ratio 1:1:1:1
A
i
B
AB
Bi
PHENOTYPES:
i
-type AB (25%); type B (25%)
type A (25%); type O (25%)
- ratio 1:1:1:1
Ai
ii
Polygenic Traits
traits produced by multiple genes
example: skin color
Sex-Linked Traits
Gene is attached to
the X chromosome
only, not found on
the Y chromosome
at all. (women have
XX, men have XY
chromosomes).
These disorders are
more common in
boys.
examples: red-green
colorblindness
Sex-Linked Traits
in males, there is
no second X
chromosome to
“mask” a recessive
gene. If they get an
X with the disorder,
they have it. Girls
must inherit
defective X’s from
both parents.
Sex-Linked Traits
A: 29, B: 45, C: --, D: 26
 Normal vision
A: 70, B: --, C: 5, D: - Red-green color blind
A: 70, B: --, C: 5, D: 6
 Red color blind
A: 70, B: --, C: 5, D: 2
 Green color blind