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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
In the case of HERDA, the mutation is likely present in all somatic cells of Polo Bueno, since the condition is inherited. However, the most critical effect would be in the cells associated with the dermis and skin connective tissues, where the symptoms of the disease are manifested.
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.
Answer
Let 'H' represent the dominant allele for non-HERDA (normal) and 'h' represent the recessive allele for HERDA. If mare II5 is a carrier (genotype 'Hh') and the normal stallion is homozygous dominant (genotype 'HH'), the potential offspring genotypes would be:
- From 'Hh' x 'HH':
- Possible Genotypes: HH (normal) and Hh (carrier)
- Expected phenotype outcomes: 50% normal horses (HH) and 50% carriers (Hh).
Based on these genotypes, the expected genotypic ratio of the offspring will be 1:1, with no offspring expressing HERDA since there are no 'hh' genotype.