Dominant and Recessive Genes in Cat Breeding (page 2)

In artificial selection, animal breeders choose the traits they want to appear in the offspring of plants or animals. For example, cat breeders are interested in a trait that controls whether ears are curved or straight. A gene that causes a cat's ear to curve inward is dominant over the recessive gene for straight ears. A dominant gene completely masks the presence of a recessive gene. Cat breeders can use their knowledge of genetics to produce kittens that display the curly-eared trait. In this activity you will simulate the breeding of two cats, one with curly ears and one with straight ears.

Materials

Small paper bag; Two red pipe cleaners (5cm long); Two white pipe cleaners (5cm long)

Activity

1. Place a red and a white pipe cleaner in the paper bag to represent the genes of a female cat. The red pipe cleaner is the dominant gene for curly ears. The white pipe cleaner is the recessive gene for straight ears.
2. Place another red and another white pipe cleaner in the same bag. These represent the genes of a male cat.
3. Close the top of the bag and shake it to simulate breeding. Without looking, reach into the bag and draw out two pipe cleaners. The pipe cleaners you have in your hand represent the genes of the cats' first kitten. Record the colors of the pipe cleaners. A red-red or red-white combination indicates that the kitten has curly ears. A white-white combination tells you that the kitten has straight ears.
4. Replace the two pipe cleaners in the bag and repeat this process seven more times. Record your results each time.

Follow-Up Questions

1. Describe the ears of the two parents.
2. How many curly-eared kittens did you produce? How many straight-eared kittens?
3. Which of the kittens could become parents of curly-eared offspring only if they mated with another curly-eared cat?

Answers

1. Both parents had curly ears.
2. Answers will vary, but the data of many students will show more curly-eared kittens than straight-eared kittens.
3. Kittens with white-white pipe cleaner combinations.

Extension

Repeat this activity, but begin with a white-white combination of pipe cleaners to represent the female and use red-red pipe cleaners for the male. Simulate breeding to produce eight kittens, then answer the follow-up questions.