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Mendel Genetics, Part 2: Codominance and Intermediate traits Objectives 
Explain what Intermediate Inheritance is, and give examples.
Explain the difference between Codominance and Incomplete Inheritance .
Perform a mono-hybrid test cross using Codominance, and analyze the Punnett Square data.
Describe what Polygenetic Traits are, and how environmental factors can affect them.
Quick reteach of important concepts
A. Genes—______________________ to do/make a particular job or characteristic. Made of 2 parts
B.
Alleles—a ______________________ of the same ________. Example: Brown, Blonde hair
C.
Phenotype—what the plant/animal ____________, based on its Genotype for that trait.
D. Genotype—The _____________________________. Caps for Dominant, lower-case for Recessive
E.
Heterozygous—2 ________________ alleles. EX: Gg
F.
Homozygous—2 _________ alleles Ex: GG or gg
What is Intermediate Inheritance?
SOMETIMES it is possible for __________________________ to create new phenotypes
(appearances) that are ______________
These ___________ traits are considered ________________________, and are the
result of gene-blending by _________________
Intermediate Inheritance, is a ‘new’ phenotype that is created when
____________________________________________________.
Intermediate Inheritance is caused by Co-dominance in genes/alleles.
(prefix ‘co’ = 2 together)
Co-dominance means that _____________ there are ______________________________ for the same trait.
If you receive ________________________, they could ________________ to create a new phenotype because neither dominates
the other.
Intermediate Inheritance examples
Example: Mice hair color genes have a __________________with ________ and _________
—meaning that ________ black and white are _____________ alleles.
___________ and ________________ ______________-is the ___________ allele in these mice.
If a mouse’s genotype is _______________________, these 2 co-dominant genes will blend together and create a mouse with a
__________________________.
In Mice, the _________ phenotype is considered an ____________________ because its phenotype is _______________________
or recessive, but rather a blend.
If the mouse genetically gained the ____________________ and a ____________________
Allele, then that rat will have patches of black and white. (co-dominance)
Example 2: Some flowers are _______________________, and if cross-pollinated
will produce heterozygous, ________ offspring. If the pink flowers are crossed,
then the offspring will be either Red or White again. (
)
Example 3: Red Hair is the ____________ of _____ pigment ________________
into another hair pigment called ____________ (the brown hair pigment)
The ‘_________________ a person’s hair is, the _____________________ and less
eumelanin there is.
_____________________ hair has ____________________, and less pheomelanin
Example 4: Green and Hazel Eyes
A. The genes that create _________ and __________ eyes are _________________. Blue eyes are Recessive
If you have heterozygous alleles of ___________ and __________, the 2 genes will _________, creating __________ eyes
If Green and Blue are heterozygous paired genes, the ________________________ the ________ gene, and the person
______________________________
Remember that the ‘true’ eye color is actually a mix of several genes working together (polygenetic traits)
Example 5: Blood types
___ and ____types are both _____________ blood type alleles. Type O is recessive.
_________ blood type is a ___________________________.
Intermediate Inheritance—How it works
Ex: Andalusian Chickens come in Black, White, or ‘Blue’.
White and Black Colors are co-dominant with each other in this species.
_________________________, created when ___________ Color _________ and a _____________ color _________ are combined
and ____________, unable to completely dominate each other.
Cross-test with Codominance
When writing these Intermediate alleles, the “C” for Color is used.
With the “C”, a superscript “W” or “B” is used to show which Intermediate alleles it has.
_________ = White
___________ = Black
________ = Blue chicken
A Punnett Square testcross is the same as a Mono-hybrid cross, but when analyzing the results, you need to look more carefully.
Intermediate Test-cross (punnett square) example
Mr. Vogel has Blood Type B. There is no type O in his family, So he is probablyhomozygous Type B
Mrs. Vogel is Type A, with some type O (recessive allele) so her genotype is probably heterozygous A and O
Both A and B are co-dominant alleles, but O type is recessive.
What are the possible outcomes of their children's’ blood type?
What are the Genotypes avaliable?
Genotypes of the Blood Types
Type A = ________ or __________
Type B = ________ or __________
Type O (recessive) = ___________
Type AB (intermediate) =________
Space provided for practice
Step 1: make the square (in the space provided)
Step 2: create the genotypes: T will be used for blood Type
Mr. V is homozygous B—so the genotype is ___________
Mrs. V. is Heterozygous A and recessive O, so the genotype is ________ (t = the recessive blood type allele)
Step 3: add the genes to the square, and do the test-cross, like normal. (do it in the space provided)
Note: if you see genotypes with both dominant traits, then they will be blended.
So, the outcomes of blood types are…
_____% A
_____% AB
_____% B
______% O
Intermediate Test-cross Example 2 (punnett square)
Snapdragons are co-dominant red and white. If these genes are combined, then they produce pink flowers.
What % of the offspring would be white if 2 Pink parents are crossed?
Step 1 – make square (this space here)
Step 2: create genotypes: C for Color is used.
--Pink is a blend of red and white so a pink’s genotype must be__________.
Step 3: add the genes to the square and do the test-cross. (do it in the space provided)
According to the data ____% of the offspring will be white, and ____% will be red.
Polygenic Inheritance
Many traits are NOT determined by ______________________.
Some phenotypes, like _________, and _____________________ are considered Polygenic, or
______________________________________________
Polygenic Inheritance Ex: Height
A person’s height may be determined by ___________________, each controlled by separate genes:
1. Length of leg-bones (_________)
2. Length of ________/vertebrate
3. Length of ________.
Since these characteristics all have their own Genotype, and are all _____________ to make a person’s total height, Height would be a
______________.
Polygenic Inheritance and the environment
Many of these traits may be affected by _____________________________as well.
Ex 1: a person’s ______________________ may say that this person ____________________, but a ____________________________
may keep the person ___________ than they could be.
In Medieval Times, a constant, _________________________ was basically impossible for people to have.
People back then ________________________ as people today, but the lack of proper diet ___________
give their bodies the nutrition needed to ___________________.
A _______________ male, which is an __________________, was considered ______________________
review Questions, Part 1
1.
What is Intermediate Inheritance? Give 2 examples
2.
How is Co-dominance different than Incomplete Dominance?
3.
ID each intermediate trait as being either Incomplete Dominance, or Co-dominance….
A. Sickle-Cell Anemia—a gene that makes red blood cells twisted is
present. The person is heterozygous with these alleles. Half the red
blood cells are twisted, and half of them are normal.
B. A rabbit’s brown fur is the result of a white fur and a red fur blending.
C.
A dog with eye patches and dog without eye patches breed and
produce heterozygous offspring with one eyepatch on their face.
D. A heterozygous flower with purple and yellow alleles. The result is
purple flowers with yellow spots.
E. A white cat and a brown cat mate and the result is a heterozygous
orange cat.
F.
4.
A child with wavy hair as a result of one parent's curly hair and the
other's straight hair
Write the genotypes for these co-dominant alleles.
A. Yellow and Red flower alleles =
B. Blood Type A and Blood Type B =
5.
Complete the test cross for these co-dominant traits.
A. Parent 1 has blood type A. Parent 2 has B type
blood. Both of these parents carry O type blood,
making them both heterozygous genotyped.
Both A and B blood types are dominant, and
combine to make AB blood type. What % of
their children will have….
A. O type
B. AB Type
6.
A multi-petal flower species has genes for Red, Blue
and White. Red and White are both dominant, and
Blue is the recessive color. When the co-dominant
Red and White combine, the flower will have both
Red and White petals.
If parent 1 is heterozygous Red and White, and
Parent 2 is Heterozygous White and Blue, what % of
the offspring will have the red/white petals?
7.
Use the same square work from #6  If a dominant Red flower allele combines with the recessive Blue allele, the flower will
look purple. What % of the offspring from #6 will look purple?
8.
What are Polygenetic Traits? Give and explain 2 examples.
9.
How would blood Type B- be considered a polygenetic trait?