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.
Answer: The salinity of the water increases
Explanation: When the moves from equator to the polar region the salty water starts freezing, the ice that is formed is not salty means it is a source of freshwater.
So, the water that reaches the poles becomes ice and the salinity of the water increases. This is because the poles are colder as compared to the other parts of the globe. The water becomes ice there and its salinity increases.
Answer:
C) The mouse CFTR gene and human CFTR gene encode proteins that can serve a similar function.
Explanation:
CFTR gene encodes for Cystic fibrosis transmembrane conductance regulator protein. It is ion channel protein and conducts chloride ions across the cell membrane. Its mutation leads to cystic fibrosis which is characterised by presence of thickened mucus in lungs with frequent infections.
In the given experiment, human CFTR gene is able to function in mouse and restore the lost body functions. This is because human and mouse CFTR gene show high level of similarity due to which they code similar proteins which can function in each other's place. However this does not mean that DNA sequence of the genes is identical. There is still some difference between them because they are two different species.
In reality human CFTR gene is around 189 kb in length whereas mouse CFTR gene is around 152 kb in length. The 27 exons have very similar sequence. Most introns of human CFTR gene are larger than the mouse counterpart.
The process by which green plants and some other organisms use sunlight to synthesize foods from carbon dioxide and water. Photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen as a byproduct.
