The purpose of a presumptive test is to see which substance the sample is.
Answer:
An experimental group, also known as a treatment group, receives the treatment whose effect researchers wish to study, whereas a control group does not. They should be identical in all other ways.
A replication bubble forms as the DNA unwinds.
Option C
<u>Explanation</u>:
Replication bubble is the space where the strands of double helical DNA structure are separated with the help of DNA helicase. The strands of the double helical DNA are still in the helix form on the both end of the unwinded DNA stand which gives this region an appearance of a bubble.
DNA unwinding is the first step in replication or transcription of the DNA molecule. DNA helicase separates the two types of "DNA" that are connected by hydrogen bonds with the help of ATP hydrolysis.
For radioactive materials with short half-lives, you use a very sensitive calibrated detector to measure how many counts per second it is producing. Then using the exact same set up you do the same at a latter time. You use the two readings and the time between them to determine the half-life. You don’t have to wait exactly a half-life, you can do the math with any significant time difference. Also, you don’t need to know the absolute radioactivity, as long as the set up is the same you only need to know fraction by which it changed.
For radioactive materials with long half-lives that won’t work. Instead you approach the problem differently. You precisely measure the mass of a very pure sample of the radioactive material. You can use that to calculate the number of atoms in the sample. Then you put the sample in a counter that is calibrated to determine the absolute number of disintegrations happening in a given time. Now you know how many of them are disintegrating every second. You use the following equations:
Decays per Second = (Number of Atoms) x (Decay Constant)
Half-life = (Natural Log of 2) / (Decay Constant)
And you can calculate the half-life
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