The “chestnut vs. black” debate Shortly after the rediscovery of Mendel’s pea plant experiments, biologists began investigating whether Mendel’s laws applied to other species, as well. In England, a debate broke out about whether the color of racehorses might be governed by Mendel’s laws. Using the British Jockey Club registry of racehorse pedigrees, biologists made the following observations: 1.A chestnut (red) stallion, when bred to chestnut mares, always produced chestnut foals. 2.Certain black stallions, when bred to chestnut mares, produced only black foals. 3.Other black stallions, when bred to chestnut mares, produced a mix of black foals and chestnut foals. Based on these observations, which is dominant: black or chestnut? 1st step: Test the two hypotheses described below. Draw the Punnett squares of the different combinations of parents (use the alleles C/c for color) one after the other, comparing your results with the observations described above. Hypothesis 1 = chestnut is dominant (cross chesnut stallions with a chestnut mare) Hypothesis 2= black is dominant (cross black stallions with a chestnut mare) Consider one hypothesis after the other. If one hypothesis is supported, then the other one is rejected. The mare (female) has one genotype, while the stallion (male) has 2 different genotypes (because it gives different foals when bred to the the chestnut female). 2d step: Results of the different Punnett squares will support one hypothesis and reject the other. 3d step: determine which color is dominant.
The “chestnut vs. black” debate
Shortly after the rediscovery of Mendel’s pea plant experiments, biologists began investigating whether Mendel’s laws applied to other species, as well. In England, a debate broke out about whether the color of racehorses might be governed by Mendel’s laws. Using the British Jockey Club registry of racehorse pedigrees, biologists made the following observations:
1.A chestnut (red) stallion, when bred to chestnut mares, always produced chestnut foals.
2.Certain black stallions, when bred to chestnut mares, produced only black foals.
3.Other black stallions, when bred to chestnut mares, produced a mix of black foals and chestnut foals.
Based on these observations, which is dominant: black or chestnut?
1st step: Test the two hypotheses described below. Draw the Punnett squares of the different combinations of parents (use the alleles C/c for color) one after the other, comparing your results with the observations described above.
Hypothesis 1 = chestnut is dominant (cross chesnut stallions with a chestnut mare)
Hypothesis 2= black is dominant (cross black stallions with a chestnut mare)
Consider one hypothesis after the other. If one hypothesis is supported, then the other one is rejected. The mare (female) has one genotype, while the stallion (male) has 2 different genotypes (because it gives different foals when bred to the the chestnut female).
2d step: Results of the different Punnett squares will support one hypothesis and reject the other.
3d step: determine which color is dominant.
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