Answer:
monoclonal antibodies
Explanation:
Monoclonal antibodies are antibodies that are made by identical immune cells which are all clones of a unique parent cell.
Monoclonal antibodies can be isolated such that they will be able to only recognize a unique epitope, this makes them to be suitable for determining the expression one or two identical sequenced proteins. Monoclonal antibodies technique is one of the most effective chromatography techniques.
Polyclonal antibodies contain different epitopes on a protein, hence suitable for protein identification but not suitable for determining the expression of one or two identically sequenced proteins.
An enzyme is a protein produced by an organism that speeds up chemical reactions
Answer:
D. They define geological periods because scientists use them as reference points for tracking the history of the earth.
Explanation:
Catastrophic events related to changes in geological timeline are very useful in defining geological periods.
These events have very significant appearance in the geological record and can be used to determine the history of the earth.
The catastrophic events usually culminates into extinction cycles or termination of some organisms from the earth surface.
Geologists use these events that are often wide spread to delineate geological periods.
