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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

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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?

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Answer

Identical twins, or monozygotic twins, originate from a single fertilized egg that splits into two embryos, thus sharing 100% of their genetic material. In contrast, nonidentical twins, or dizygotic twins, arise from two separate eggs fertilized by two different sperm cells, sharing about 50% of their genetic material. Therefore, the main difference lies in the degree of genetic similarity.

Step 2

b. Fill in the missing percentages of twin pairs that both develop asthma in column D of the table above.

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Answer

For the monozygotic twins, 50% develop asthma, while for the dizygotic twins, only 25% do. This can be calculated as follows:

  • For monozygotic twins: D=BA×100=2550×100=50%D = \frac{B}{A} \times 100 = \frac{25}{50} \times 100 = 50\%
  • For dizygotic twins: D=BA×100=25100×100=25%D = \frac{B}{A} \times 100 = \frac{25}{100} \times 100 = 25\%

Step 3

c. From these results, are identical twins more or less likely to share a tendency to develop asthma than nonidentical twins?

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Answer

Identical twins are more likely to share a tendency to develop asthma. The results from the table indicate that while 50% of monozygotic twins both develop asthma, only 25% of dizygotic twins do. This suggests a stronger genetic component in the likelihood of developing asthma among identical twins.

Step 4

d. Prior to this study, the researchers believed that asthma was an inherited condition. However, following the study, they concluded that both genetics and the environment were factors. What evidence from the data suggests that the environment has a role in the development of asthma?

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Answer

The data indicates that 50% of identical twins do not develop asthma, despite being genetically identical. This suggests that other factors, likely environmental, play a significant role in the development of asthma, as the cases among the identical twins cannot be solely attributed to genetics.

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