Warm- Up
If the pedigree shows the disorder
hemophilia caused by a recessive
allele (h)…
1.What is the genotype of
person 1?
2.What is the genotype of
person 2?
3.What is the phenotype of
person 4?
Review
• A couple wants to know how likely
their children will inherit a form of
deafness, which is caused by a
recessive gene. The mother has
no family history of deafness, but
the father is heterozygous for the
deafness. Use the letter “D” to
complete the Punnett Square
People in a town of Alaska have seen some
wolves with black coats and blue eyes recently.
They want to know how likely it is for a wolf to
have both traits. Normal coat color (N) is dominant
to black (n) and brown eyes (B) are dominant to
blue (b). The alpha male is black with blue eyes
and the alpha female is heterozygous for normal
colored coat and for brown eyes.
What are their genotypes?
a.
How many of the offspring out of 16 living in the
pack will have a normal coat and brown eyes?
b.
How many of the offspring out of 16 living in the
pack will have a black coat and blue eyes?
Sex-linked trait
A boy, whose parents and grandparents
had normal vision, is color-blind. What
genotype must his mother have in order
for him to have color-blindness? Use XB
for the dominant normal condition and Xb
for the recessive, color-blind phenotype.
A woman is concerned that her children may
inherit cystic fibrosis, which runs in her family.
She does not have the disorder herself, but she
may be a carrier.
1.What would her genotype look like if she is a
carrier? (use the letter F)
2.What is the probability that she would have a
child with cystic fibrosis?
Warm Up
1. Name two diseases that are sex-linked (found on the Xchromosome)
2. Name two diseases that are autosomal.
3. In the pedigree below, is the trait autosomal or sexlinked?
1. Which type of inheritance involves
multiple genes?
2. Which type of inheritance leads to a
blend of two traits?
Bellwork: Inheritance Patterns
• When multiple alleles code for a trait it
is called a _________________ trait.
Warm Up
1.
2. When two traits are equally expressed
in an organism, the mode of
inheritance is ___________________
How do we inherit traits?
a) The different ways that people inherit
traits are called “modes of
inheritance”.
b) There are 4 modes of inheritance that
you will need to know:
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Complete Dominance
Incomplete Dominance
Codominance
Polygenic Traits
Complete Dominance
• This is when one trait overpowers
another.
• The dominant trait is the one that will
suppress other traits. (BB or Bb)
• The recessive trait is hidden unless
there are two copies of the allele
present in the gene. (bb)
What is Incomplete
Dominance?
a) Incomplete dominance is when the offspring
have a blend of their parents’ traits.
b) Example: If red snapdragons (RR) are crossed
with white snapdragons (rr), you get PINK
snapdragons (Rr)!
c) The genotypes would be Rr but the flowers will
be pink because both traits blended to form a
new phenotype.
Example of Incomplete Dominance
What is Co-dominance?
a) Co-dominance is when the two different
alleles are equally expressed in a
heterozygous offspring.
b) Both alleles makeup the phenotype without
blending together.
c) Example: Not all things in the world are just
black or brown! Lots of things are spotted
or made of multiple colors due to codominant traits.
Co-dominance
What are Polygenic traits?
a) Polygenic traits are traits controlled by
two or more genes
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b)
“Poly” means many or multiple
Polygenic traits often show a wide variety
of phenotypes.
c) This type of inheritance is responsible for
the wide range of different skin colors in
humans. There are more than 4 different
genes that determine this trait.
Polygenetic traits
Examples in Humans
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•
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•
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Eye color
Height
Weight
Skin Color
Blood Type
Multiple Alleles
a) When there are more than two
possible alleles for a trait, it’s called
multiple allele inheritance
b) In a population, there are multiple
alleles that can make up a trait
c) Example: Blood Type
-
People can have the blood types A, B,
AB or O
Blood Types
Blood Type Practice
Example problem
Andalusian chickens can come in
different colors. When a black chicken is
crossed with white chicken, they
produce a “blue” chicken. The blue
Andalusian chicken is called blue
because it has both black and white
feathers. What type of inheritance is
this?
Practice Problems
Exit Ticket
1. A cat is spotted. It has white fur and orange
spots. What mode of inheritance is it
expressing?
2. A red rose and a yellow rose are crossed
and they produce orange offspring. What
mode of inheritance is this?
3. Skin color is an example of what mode of
inheritance?
Mode of Inheritance
Suppose you have two rose plants, both
with pink flowers. You cross the two
plants and are surprised to find that, while
most of the offspring are pink, some are
red and some are white. What type of
inheritance is this? (incomplete, codominance, multiple alleles, polygenic,
sex-linked)?