Canine Case studies
Part 1: Doggie dilemma
Now that Jessica is out of college and living on her own, she has decided to
get a dog. She would like to buy a puppy from a breeder because she wants to make
sure she gets a purebred dog. Jessica has always wanted a Boston Terrier and after
some research, she found a breeder outside of Philadelphia. In a few months, Jessica
brought her Boston Terrier puppy home. She named him Houston. Houston was a
healthy puppy but when he turned one (in human years) he developed a luxating
patella. Luxating patella is a condition in which the knee cap (or patella) dislocates
out of its normal position causing a lot of pain. The only option was surgery.
Jessica was curious as to why her dog developed this condition and after
talking to her Veterinarian, she was told that it is usually genetically linked and can
be prevented by avoiding inbreeding in most cases. Jessica immediately called the
breeder and the breeder told her that there were no cases of luxating patella in all
the years he had bred Boston Terriers. The breeder, however, was willing to send a
pedigree of the past few generations of Houston’s family. Below is the pedigree that
Jessica received in the mail from the breeder.
Houston is
number 73543.
He is shaded in
because he has
luxating patella.
The breeder did
not want to reveal
the names of his
dogs so numbers
were assigned.
Answer the following questions about Houston’s pedigree
1. Do any other dogs in this pedigree have luxating patella?
2. Do you think it is a recessive or dominant condition? Explain.
3. What numbers represent Houston’s parents?
4. What would be the genotypes of Houston’s parents? Explain.
5. What numbers represent his paternal grandparents?
6. What numbers represent his maternal grandparents?
7. How many offspring did parents 2230 and 2369 have?
a. How many were males?
b. How many were females?
8. What two relationships exist between numbers 69520 and 54533?
9. What two relationships exist between numbers 69518 and 69535?
10. Explain how Houston’s father is related to his mother. (other than just being
a mating pair)
11. Based on your answers above, do you think inbreeding caused Houston’s
luxating patella? Explain.
12. Do you think Jessica should call the breeder and share the information she
found with him? Explain.
Part 2: Doggie Food Forensics
About 2 months after the surgery, Houston made a full recovery. He was
back to playing Frisbee and going for long walks. But this was not the end of
Jessica’s dog problems. One day in the mail she received an urgent letter from the
FDA stating that the dog food brand, PuppyGro, she has been purchasing may
contain “illegal meat” and further testing on the food was necessary. She was told in
the letter to not use PuppyGro until more information was obtained. Jessica could
not even imagine what illegal meat could be in her food. The labels said beef and
chicken, but what can be illegal about that?
Back in the FDA lab, scientists and other researchers were working on a
study to find out what illegal substances were in PuppyGro. PuppyGro, which is
manufactured in Japan, has always had a good reputation, until recently an inside
source shared that they were using whale and shark meat in their food products
instead of the advertised chicken and beef.
The first thing researches wanted to do was eliminate possible whale and
shark species that could have been used based on location (even though it is
possible shark and whale meat could be imported from somewhere else around the
world).
Use the map data sheet to answer the following question
1. Based on the maps, which whales and sharks would Japan possibly capture
and use in their dog food products? Explain your answer.
The next step was to extract DNA from the PuppyGro dog food. They used
another dog food (named dog food brand X) that did not have illegal meat as a
control and extracted DNA from that dog food as well. Once the DNA was
extracted, it could be sequenced. The scientists only wanted to sequence the
animal DNA. The sequences of the DNA from each food sample are found on the
DNA sequence data sheet. There were two different DNA samples extracted
from each dog food brand.
Use the DNA sequence data sheet to answer the questions below
1. What was the purpose of the control?
2. Using teacher instructions on how to use BLAST, identify the organisms in
which the DNA sequences belong.
a. What animal meat was used in the control dog food (brand X)?
b. What animal meat was used in the PuppyGro brand?
3. Why do you think certain companies would use whale and shark meat over
chicken and beef in their dog food products? Do you think they purposely kill
whales and shark for their meat?
4. Below is a graph that shows the number of sharks killed by fishnets
UNINTENTIONALLY. Answer the questions that follow.
a. Approximately what year was the number of sharks caught in nets the
largest?
b. Why do you think the number of sharks caught in nets has started to
decrease?
c. What do you think fisherman do with sharks that die from being
caught in fishnets?
d. Could this data be used to help understand why companies may use
shark meat in dog food?
A few months after receiving her first letter from the FDA, Jessica
received a second letter explaining that they did find illegal meat in
PuppyGro. Production of that dog food brand would stop immediately.
The illegal meats that were in the PuppyGro dog food would not harm her
dog.
Application
1. Do you think DNA sequencing technology can be used to identify plant
species in dog food? Explain.
2. Do you think DNA sequencing can be used to detect food pathogens such
as bacteria? Explain.