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The quarter horse, as a breed, originated by selective breeding - VCE - SSCE Biology - Question 5 - 2011 - Paper 1
Question 5
The quarter horse, as a breed, originated by selective breeding. The first Australian quarter horses were imported from North America in the 1950s. A genetic conditi... show full transcript
Worked Solution & Example Answer:The quarter horse, as a breed, originated by selective breeding - VCE - SSCE Biology - Question 5 - 2011 - Paper 1
Step 1
a. Which cells in the body of Polo Bueno were affected by the mutation allowing HERDA to be inherited?
Answer
The cells affected by the mutation responsible for HERDA in Polo Bueno are likely the dermal cells. This genetic condition primarily affects the skin and connective tissues, therefore the skin cells are the most affected.
Step 2
Step 3
c. After the horses arrived in Australia, mare II5 is mated to a normal stallion from a different family with no family history of HERDA. Using appropriate symbols for genotypes, show all possible outcomes of this mating. Include the phenotypes and genotypes of parents and foals.
Answer
To represent the genotypes:
- Assume mare II5 is a carrier for HERDA, hence her genotype is Hh (where H = normal, h = affected).
- The stallion is normal and has no history of HERDA, so his genotype is HH.
Possible offspring genotypes:
- HH - Normal
- Hh - Carrier
Using a Punnett square representation:
| H | H | |
|---|---|---|
| H | HH | HH |
| h | Hh | Hh |
Phenotypically:
- 50% Normal
- 50% Carrier for HERDA
Thus, the offspring will either be normal or carriers but none will express the disease.