Download Non-Mendelian Genetics

Non-Mendelian Genetics
Non-Mendelian Genetics
• Some traits don’t follow the simple
dominant/recessive rules that Mendel first
applied to genetics.
• Traits can be controlled by more than one
gene.
• Some alleles are neither dominant nor
recessive.
Incomplete Dominance
• One allele is not completely dominant
over another.
• The heterozygous phenotype is a
blending of the two homozygous
phenotypes.
Example: four o’clock flowers
• rr=red
• ww=white
• rw=pink (blending of the two alleles)
Check for Understanding:
Spongebob and his friend, Patrick, love to
go jellyfishing at jellyfish fields! The fields
are home to a special type of green jellyfish
known as Goobers. Many of the Jellyfish are
yellow (YY) or blue (BB), but some end up
green because of incomplete dominance.
What is the genotype of a “Goober” green
jellyfish?
What would happen if Spongebob
and Patrick crossed two “Goober”
green jellyfish? Complete the
punnett square to determine the
offspring phenotypes.
What would happen if they crossed
a yellow jellyfish (YY) with a
“Goober” green jellyfish? Complete
the punnett square to determine
the color of the offspring.
Codominance
• Two alleles are both
expressed as a
dominant phenotype
• Ex: Coat color in
cows
– RR: Red
– WW: White
– RW: Roan, white with
red spots (NOT pink!)
Check for Understanding:
How is codominance different from
incomplete dominance?
In some cats, the gene for fur color is
codominant. The allele for black is B
and the allele for orange is O. The
heterozygous phenotype is known as
calico.
What is the genotype for black cats?
What is the genotype for orange cats?
What is the genotype for a calico cat?
If two calico cats were crossed,
what is the probability of having
an all black kitten? Use the
punnett square to determine the
probability.
Multiple-Allele Traits
• Codominance
• More than two choices of alleles are present for a
trait
• ABO blood type has three alleles
• ABO Blood types:
– If both A and B are present, type is AB
– Neither is recessive
• Individuals can be type A, B, AB, or O (recessive)
What is blood made up of?
• The red blood cells
– contain hemoglobin.
– Red blood cells transport O2 and CO2
to and from body tissues.
• The white blood cells
– fight infection.
• The platelets
– help the blood to clot
• The plasma
– Fluid which contains salts and
various kinds of proteins.
Determining Blood Type
• Protein molecules found on the surface
of RBC’s and in the blood plasma
determine the blood type of an individual.
– Antigens are located on the surface of the
red blood cells
– Antibodies are in the blood plasma.
What are the different blood
groups?
• Blood group A (IA, IA ), (IA, i)
have A antigens on the surface
of red blood cells and B
antibodies in blood plasma.
• Blood group B (IB, IB ), (IB, i)
have B antigens on the surface
of red blood cells and A
antibodies in blood plasma.
What are the different blood
groups?
• Blood group AB (IA, IB )
have both A and B antigens on the
surface of red blood cells and no A or B
antibodies in blood plasma.
• Blood group O (i, i)
have neither A or B antigens on the
surface of red blood cells but have both A
and B antibodies in blood plasma.
Blood transfusions – who can
receive blood from whom?
• The transfusion will work if a person who
is going to receive blood has a blood
group that doesn't have any antibodies
against the donor blood's antigens.
• People with blood group 0 are called
"universal donors" and people with
blood group AB are called "universal
receivers."
Sex-Linked Inheritance
Review
• Males have an X and a Y
chromosome
• Females have two X
chromosomes
• These chromosomes determine
sex, so genes located on these
chromosomes are known as
sex-linked genes.
• The X chromosome is
much larger than the Y, so
it carries more genes than
the Y chromosome, so
sex-linked genes are
always carried on the X.
•Disorders that are sex-linked are much
more common in males, because they
would only need 1 recessive allele to have
the trait; rather than the two recessive
alleles the females need.
Hemophilia
• Recessive trait
• Disorder where individuals are missing the
normal blood clotting protein.
• Uncontrolled bleeds from minor cuts or
bruises.
• Female genotype with Hemophilia:
• Male genotype with Hemophilia:
Colorblindness
•
•
•
•
Recessive
Inability to see certain colors
Female genotype with Colorblindness:
Male genotype with Colorblindness:
Duchenne Muscular Dystrophy
• Recessive
• Progressive weakening and loss of
skeletal muscle.
• Defective version of gene that codes for
muscle protein
• Female genotype:
• Male genotype:
Check for Understanding:
• A woman who is heterozygous for normal
vision (XBXb) marries a man who is
colorblind (XbY). What are the chances of
them having a son or daughter who is
colorblind? Remember: Colorblindness is
a recessive trait.
• A woman who is homozygous (XHXH) for
normal blood clotting marries a man who
has hemophilia (XhY). What are the
chances of them having a son or daughter
with hemophilia?
SOURCES CREDITED TO:
CASTLE HIGH SCHOOL &
JOHN HOPKINS MEDICAL
INSTITUTE