Transcript 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)
Codominance
• Two alleles are both
expressed as a
dominant phenotype
• Coat color in cows
– RR: Red
– WW: White
– RW: Roan, white with
red spots (NOT pink!)
Multiple-Allele Series
• 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."
Rh Factor
• Refers to another antigen on red blood
cells
• Dominant trait is to have the antigen
– Rh+
• Recessive trait is not to have it
– Rh-
• A person with Rh- blood will produce
antibodies to Rh+ blood
• Can be a problem in pregnancy
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.
•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:
• Male genotype:
Colorblindness
•
•
•
•
Recessive
Inability to see certain colors
Female genotype:
Male genotype:
Duchenne Muscular Dystrophy
• Recessive
• Progressive weakening and loss of
skeletal muscle.
• Defective version of gene that codes for
muscle protein
• Female genotype:
• Male genotype:
• EXAMPLES!!
• A woman who is heterozygous for normal
vision marries a man who is colorblind.
What are the chances of them having a
son or daughter who is colorblind?
**NOTE: You have to use X’s and Y’s, and
read the punnett square separately for
boys and girls!**
• A woman who is homozygous for normal
blood clotting marries a man who has
hemophilia. What are the chances of
them having a son or daughter with
hemophilia?