Can mushers use the science of genetics to get the winning Iditarod dog?
Science, genetics, math
Today, for competitive dog mushers in the Iditarod, five key traits are desired and selectively bred for in a husky: moderately dense coat for protection in arctic weather while also allowing the escape of excess heat, durable feet, a physiology adapted to high calorie intake of food, a pulling enthusiasm, and an ability to comfortably change gaits from a walk, trot, and lope.
Despite their mixed genetic heritage and careful performance-driven breeding, Alaskan huskies still maintain common physical traits. The best racing dogs have quick, efficient gaits and remarkable strength for their size. They range most often from 40 to 70 lbs. Their lean bodies specially adapted for enduring long runs of up to 150 miles while maintaining long-haul speeds around 9 miles per hour.
Prior to the activity, create six genotypes cards, three for each gender. One card should be of excellent quality genotype, one should be of medium quality genotype, and one should be of poor quality.
1) Share with your students that this is a game activity that will have them act as a musher trying to breed the best possible sled dogs to win the Iditarod over the course of three generations. You will be the 2013 Champion musher, Mitch Seavey, during the activity. Students will come to you to buy breeding; when doing so they take a chance at picking a genotype card. Students will also have to pay teacher if they choose to inbreed.
2) As an introduction to the racing sled dog genetics read as a class or individually “Beringia Sled Dog”
3) Students work in teams of 3-4 students refreshing their prior knowledge about principles of inheritance and how to identify and work with genotypes, phenotypes and genetic probability. Have teams share and summarize the principles as a class.
4) Looking to the “5 Key Traits” each team work together to generate the chart that displays rules of inheritance governing the key traits for the sled dogs (medium coat thickness, durable feet, high calorie intake, pulling enthusiasm, ability to change gaits). This will ensure familiarity and understanding of traits as a premise of a good game.
5) Provide each student with Five “Iditarod Dollars” (this can be anything from monopoly money to buttons). Provide the students each with a coin and a dice. Students keep records and track of score in notebook.
6) Let the breeding begin!
7) Discuss the game results as a class. Have students answer to the leading question if “Can mushers use the science of genetics to get the winning Iditarod dog?” – Why, why not?
What are other factors that mushers would consider in breeding than the here used traits? What are other factors that make up a winning Iditarod sled dog, other than genetics?
Activity adapted from Science teacher Sid Lucas.
5 Key Traits
Medium Coat Thickness
Rules of inheritance: Incomplete dominance (K,k)
Possible genotypes point system: KK = 2, Kk = 3, kk = 1
Rules of inheritance: Codominance (B,W)
Possible genotypes point system: BB = 3, BW = 2, WW = 1
High Calorie Intake
Rules of inheritance: Simple dominance (H,h)
Possible genotypes point system: HH = 3, Hh = 2, hh = 1
Rules of inheritance: Multiple alleles (T,P,O)
Follow rules of blood genetics: A, B, O –
Possible genotypes point system: TT = 2, TP = 1, TP = 3, PP -= 2, PO = 1, OO = 0
Ability to Change Gate
Polygenic Inheritance (D, d, E, e, F, f)
Possible genotypes point system:
Range: DDEEFF to ddeeff. Total score for Polygenic Trait is the sum of the values for each gene. Example: DDEdff = 3 points.
Homozygous Dominant = 2, Heterozygous = 1, Homozygous Recessive = 0
Game Guide Lines
You are a musher breeding your own dogs. You must breed 3 generations with the goal to breed the dog with the most desirable genotype. You have a budget of $5. You can breed two offspring per breeding pair, one male and one female. You must always breed a puppy of previous mating. You want to try to avoid inbreeding, you will financially punished if you do it, and doing so more than once will have you disqualified. At a cost, you are allowed to take a chance and buy a dog straight from an Iditarod Champion once or as many as you want from some other musher for you to breed with. You can not sell a dog you have used for breeding; and you can not re-sell – you can only sell un-bred dogs born in your kennel. Two mushers can only deal ‘one-way-, one time. At the end of the game you earn 1 point, per one dollar left in the budget.
Cost of breeding:
1st generation = free
Inbreeding = $4
Buy a Iditarod Champion dog (one-time limit) = $3
Buy another musher’s dog = negotiate cost, minimum $1
You earn point according to the Genotype Scoring Chart – 0 to 3 points earned per value for each gene.
The Pulling Enthusiasm trait is determined by the role of a dice:
1 and 4 = T, 2 and 5 = P, 3 and 6 = O
All other traits are determined with the flip of a coin.
Beringia Sled Dog
The history of sled dog begins maybe some 10,000 years ago in Beringia. The oldest remains of sled dogs, more than 7000 years old, are found in Chukotka. The sled dog spread froom Chukotka across Beringia when peoples crossed the Bering land bridge from Asia into North America.
The husky was traditionally bred as a draft animal used for hunting and transportation, primarily pulling freight.
In Alaska, in the 1890’s, During the Alaskan gold rush, teams of huskies were used for pulling miners and their gear to remote camps. However, the demand for dogs during this time was greater than the supply so other strong, pulling breeds were brought north from the southern states and sold to desperate miners. By 1908, miners and other northern dwellers had begun to race sled dogs for sport and entertainment. At the same time more dogs – Chukchi dogs – were brought over from the Russian side of the Bering strait, from Chukotka to compete. They were nick-named Siberian rats because they were smaller in stature. Soon these dogs dominated racing entirely, their records still standing today. These dogs included the famous Iditarod Serum run dog: Togo and Balto run by the Norwegian musher Sepalla. It is from this line of dogs we now have the pure-bred Siberian Huskies. The Siberian Huskies that trace back to the original dogs brought over at that time from Chukotka are called Seppala Siberian Huskies.
From that time on, the competition lead to the selective breeding of Alaskan husky racing dogs in Alaska and to what we know them as today.
The Chukchi dog too has evolved over time through breeding, but believed to one of Earth’s Basal Breeds it is predominantly an “original dog.” There are only believed to be 7 sch basal Breeds in the world today.