When you start the PCR amplification reaction, you have a template which has sequences where the primers will anneal. The forward primer anneals in the sense strand and the reverse one in the complementary sequence (see attached figure).
After the first PCR cycle, two types of fragments are obtained. First those which come from tha 5'-3' sequence, that are 3'-5' and will anneal the reverse primer in the following cycle. This fragments have the correct 3' end, but the 5' includes part of the template that doesn't correspond to our target (see attached figure)
Second, those fragments that come from the 3'-5' sequence, that are 5'-3' and will anneal the forward primer. This fragments also have the correct 3' end, but the 5' includes part of the template that doesn't correspond to our target (see attached figure).
Now, during the second cycle, are produced the first fragments that have the precise length of the sequence that we want to amplify (see attached figure).
So, it's not until the third cycle that the reaction starts amplifying exactly the sequence of desired length.
<h2>Correct Answer is option "d"</h2>
Explanation:
- Heroine is an drug of opiod plant which is made up of from morphine,a natural substance which taken from the seed pod of the different opium poppy plants.
- Heroine is found in various form such as in white powder and brown powder.
- Other common names for heroine are horse,smack & hell dust.
- People takes heroine in different route of administration such as few people smoke it, some inject, or other used as sniff etc.
- Heroine enter in brain rapidly and combined with opiod receptors on cells ,it involve in pain and pleasure,controlling heart rate etc.
- It show both effects short term and long term effect on the brain and body.
- Hence, the correct answer is option d "Heroine"
I personally think that it's D. If this is right you're welcome. If it's wrong feel free to delete this answer :p