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Asthma can be a serious medical condition that affects over 2.2 million Australians - VCE - SSCE Biology - Question 6 - 2004 - Paper 1
Question 6
Asthma can be a serious medical condition that affects over 2.2 million Australians. People with asthma may experience shortness of breath and wheezing due to narrow... show full transcript
Worked Solution & Example Answer:Asthma can be a serious medical condition that affects over 2.2 million Australians - VCE - SSCE Biology - Question 6 - 2004 - Paper 1
Step 1
a. In terms of genetic variation, how are identical twins different from nonidentical twins?
Answer
Identical twins (monozygotic) originate from a single fertilized egg that splits into two, sharing 100% of their genes. In contrast, nonidentical twins (dizygotic) come from two separate eggs fertilized by two different sperm cells, sharing approximately 50% of their genes. This genetic similarity in identical twins makes them more likely to exhibit similar traits and conditions, such as asthma.
Step 2
b. Fill in the missing percentages of twin pairs that both develop asthma in column D of the table above.
Answer
For the monozygotic twin pairs, the percentage can be calculated by the formula:
ext{Percentage} = rac{ ext{Number of twin pairs that both develop asthma}}{ ext{Total number of twin pairs}} imes 100
For monozygotic twins: ext{Percentage} = rac{25}{50} imes 100 = 50\%
For dizygotic twin pairs: ext{Percentage} = rac{25}{100} imes 100 = 25\%
Thus, the missing percentages are:
- Monozygotic: 50%
- Dizygotic: 25%
Step 3
c. From these results, are identical twins more or less likely to share a tendency to develop asthma than nonidentical twins?
Answer
Identical twins are more likely to share a tendency to develop asthma than nonidentical twins, as indicated by the higher percentage of monozygotic twins who both develop asthma compared to dizygotic twins. In the study, 50% of identical twins had both developed asthma, whereas only 25% of nonidentical twins exhibited this trait.
Step 4
d. What evidence from the data suggests that the environment has a role in the development of asthma?
Answer
The data suggests that environment plays a role in the development of asthma because even among identical twins, who share the same genetic makeup, only 50% develop asthma. This indicates that external factors, potentially environmental, contribute to the condition since the remaining 50% do not have asthma despite their genetic similarity.