Screencast Tutorial
Cats have genes too…
19 pairs of chromosomes to be exact, each with thousands of
genes that determine the physical traits. Use what you have
learned about heredity (including codominance, incomplete
dominance, and complete dominance) to answer the questions
on the cats pictured below.
The alleles you can use for the traits are listed here:
Black: B
White: W
Polydactyl: P
Siamese: S
Regular-toed: p
Long hair: h
Short hair: H
Burmese: E
One task you have today is to determine which type of dominance is shown.
Remember:
*COdominance--both alleles can be observed in heterozygotes (Think spotted!)
*Incomplete Dominance--neither allele can be observed in heterozygotes (They are
blended together!)
*Complete Dominance (the original! what we learned with the genetic baby
assignment)--the recessive (a lowercase letter) can be hidden
Example 1
Phenotypes: Black, white, gray (silver)
Alleles: B and W
A student, recognizing that black,
gray, and white coats exist,
hypothesizes that gray coats are a
result of incomplete dominance. She
then finds that __________(name of
cat at left) and ___________(name of
cat at right) have gray baby kitten
________________(name of kitten below).
Is it possible that this is an example of incomplete dominance if two black cats have a gray
kitten? Explain.
Type of Dominance: Is it incomplete as hypothesized?
Possible genotypes for cat at left:
Possible genotypes for cat at right:
Possible genotypes for offspring:
Possible phenotypes for offspring:
Answer to question:
Example 2
Phenotypes: Piebald spotted, white, black
Alleles: B and W
___________(name of cat at left) and
___________ (name of cat at right) have their
spotted coats as a result of codominance.
If these two cats had offspring, what is the
percent chance that their kitten would look like
__________ (name of cat below) who is all
black? Explain.
Type of Dominance:
Possible genotypes for cat at left:
Possible genotypes for cat at right:
Possible genotypes for offspring:
Possible phenotypes for offspring:
Answer to question:
Example 3
Phenotypes: Polydactyl and regular-toed
Alleles: P (polydactyl) and p (regular-toed)
____________ (name the cat at
left), is a polydactyl cat with extra
toes. This is a dominant trait; the normal 4 toes on front limbs and 5 toes on the hind limbs is
recessive. If he was crossed with ____________ (name the cat at right with 6 toes), is it
possible that their kittens could have normal toes? Explain.
Type of Dominance: complete dominance
Possible genotypes for cat at left:
Possible genotypes for cat at right:
Possible genotypes for offspring:
Possible phenotypes for offspring:
Answer to question:
Example 4
Phenotypes: Long hair and short hair
Alleles: h (long) and H (short)
____________ (name the cat),
pictured at the left, is
long-haired. This is a recessive
trait. ________ (name of cat),
pictured right, claims that the
kitten below is his. Based on
hair length alone, is this
possible? Explain.
Based on hair length alone, is this possible? Explain.
Type of Dominance:
Possible genotypes for cat at left:
Possible genotypes for cat at right:
Possible genotypes for offspring:
Possible phenotypes for offspring:
Answer to question:
Example 5
Phenotypes: Siamese, Burmese, and Mink
Alleles: S (Siamese) and E (Burmese)
Not only do genes control what and how
much pigment is made, they also control
where the pigment goes in the body.
Siamese cats like
____________________ (pictured at the
left) have a gene that moves the
pigmentation to the “points” of the body.
(This is called the “pointed” gene.)
Burmese cats, like
_____________ pictured right, have another allele for the same gene as
the Siamese pointed gene, but it results in a reduction of pigmentation
throughout their bodies. These make cats that would have a black coat
appear brown (also known as “sepia”).
Mink cats are a blend of the siamese and burmese alleles. These result in
the reduction of pigment like the Burmese and a darker coloration of the
feet and face like the Siamese.
If a mink cat has kittens with another mink cat, is it possible that the kittens will be siamese?
Explain.
Type of Dominance:
Possible genotypes for cat at left:
Possible genotypes for cat at right:
Possible genotypes for Parent 1:
Possible genotypes for Parent 2:
Possible genotypes for offspring:
Possible phenotypes for offspring:
Answer to question:
More info on cat genes:
http://www.vgl.ucdavis.edu/services/coatcolorcat.php
http://felinegenetics.missouri.edu/feline-genome-project-2/cat-genomic-resources-karyotypes