There is no answer that is right except for C. Natural Selection.
Genetic Recombination doesn't change gene frequency;nor does migration. (Unless it's local)
Mutation could be the answer, but since mutations are too rare to really power Evolution, the only logical answer is Natural Selection.
1. is the second answer I believe and 2. is the first answer
I hope this helps
Answer:
Methotrexate inhibits the synthesis of DNA, RNA, and protein synthesis of the cells in the experiment.
Explanation:
Methotrexate competitively inhibits the enzyme dihydrofolate reductase (DHFR) which is involved in the synthesis of tetrahydrofolate from the inactive dihydrofolate. The methotrexate blocks the enzyme by binding to its active site thereby preventing further reaction of the dihydrofolate reductase enzyme and dihydrofolate. Tetrahydrofolate is a useful material for the de novo synthesis of thymidine, a nucleoside. And without thymidine, DNA synthesis is hindered. Methotrexate therefore inhibits the synthesis of DNA, RNA, thymidylates and of course protein synthesis.
The hydrosphere is comprised of all the water on a given planet.
This includes all water on the surface, underground, and in the air, including water in its liquid, vapor, or ice forms.
On Earth, for example, some parts of the hydrosphere include water vapor in the air, water in the oceans, and groundwater in wells, along with much more.
