I remember the secondary structure by visualizing it. Understand that primary structure is just the order of the amino acids. The tertiary structure is the 3dimensional configuration of the whole protein molecule with multiple interactions guiding its fold (disulfide bonds, ionic interactions, hydrogen bonds, van der walls). Secondary structure is a step towards the conformation of the protein where it is made up of either alpha-helices or beta-pleated sheets. The alpha helices look like a spiraling staircase while the beta-pleated sheets look like a repetition of long loops. These two structures hold itself by hydrogen bonds.
I am more of a chemistry person, but my best answer is the double-helix structure. The DNA rotate around a central point allowing it to keep a constant distance
The answer is D. For producing recombinant, first you need to cut the insert part and vector part to get the same end by using restriction enzyme. Then using DNA ligase to bind these two parts to get a new plasmids.
3 is the correct answer. Let me know if you want me to explain why that is the answer.
