Answer:
2.5 mg
Explanation:
<em>The half-life of a substance is the time required for one half of the substance to decay. In order words, it is the time it will take for a substance to decay into half of its initial size.</em>
For a 20 mg element with a half-life of 30 which decays over a period of 90 years;
The first 30 years, 10 mg would have decayed, remaining 10 mg
The second 30 years, the remaining 10 mg would have decayed to 5 mg
The third 30 years, 5mg would have decayed to 2.5 mg.
Hence, in 90 years, 20 mg of the element would <u>remain only 2.5 mg.</u>
Marfan syndrome can be caused by a substitution mutation in the FBN1 gene. This mutation is likely a harmful mutation.
From the DNA sequence of unaffected individual and
individual with Marfan syndrome we can see that C is substituted with G. Each parent with the Marfan syndrome has a 50% risk of passing the genetic defect on to offspring because of its autosomal dominant nature, so the mutation is harmful.
40% of the population was killed by the black death
